Summoned as a witness in a criminal case

I'm just wondering where I stand here,
Got a letter in the post today saying "Vorladung als Zeuge", asking me to come to a certain police station at a certain time this week.
It stems from an incident the night of the Turkey v Germany match, I was standing near the Burger King by Zoo with a friend when a small firework came out of nowhere and hit me in the T-Shirt/arm. Obviously quite shocked and annoyed by this, when I saw the police arrest the guy who had let it off(it was one of the ones that let off multiple fireworks, my friend said that he might have thrown it on the ground thinking it was finished). I went over and asked him what he thought he was doing, to which the police asked what I had to do with it and I told them that it had hit me. It wasn't a big one, I wasn't that injured(tiny burn on my arm and t shirt), I was just annoyed. He took down both my and my friend's details(wrongly) in the middle of the street whilst we were surrounded by a group of the guy's friends, who weren't very happy. We asked the police if they could give us a hand getting out of there to which they basically said, sorry lads you're on your own.
I totally forgot about the incident, my friend has since gone back home, I'm heading home in a few weeks after my year studying here, I had a great time here and don't want to ruin the end of it by having to appear as a witness against somebody for something that in hindsight Im really not that bothered about anymore. It was a matter of wrong place at the wrong time, and whilst it could have been worse, it wasn't.
What options do I have here, I have already gone to my local police station and asked, only to be told that it was nothing to do with them, and also to the one that I am supposed to go to but I am still none the wiser.
Any advice would be appreciated

Go to the police station carrying valid ID and answer any questions they ask.
Do not volunteer information.
Do not share your opinions or emotions.
Do not think.
Tell the truth as far as you're asked for it.
Fall back on the general chaos that ensued and the length of time that has passed since then.
Tell them when you're leaving and give them a forwarding address (Downing Street 13 in Edinburgh might work).
If your German is insufficient ask them to provide an interpreter, it's your right.

If the case goes to court they will hardly fly you back unless the guy seriously injured others. You may, however, be interrogated in the UK on behalf of the German authorities.

Just a word to the wary - when I had to give several statements to the police a few years ago, I made use of the "interpreter" (and I use that term lightly). Luckily, I was also accompanied in the first instance by a native German-speaking friend, and in the second instance by my bilingual lawyer.

I am not exaggerating when I say this - after at least every second sentence the interpreter translated for the cop taking my statement, my friend or lawyer said, "That's not right. That's not what she said." Etc. etc. In one case, the interpreter translated a crucial piece of information to mean that I was accepting fault for the incident that happened. Which was of course, the complete opposite of what I said.

Perhaps I had a bad luck of the draw, but it was very clear to me that the "interpreter" had absolutely no formal training. Honestly, it felt like they just grabbed the nearest secretary who spoke "some" English. Because your statement is being written down and you have to sign it at the end, and swear under threat of penalty that it is a true and accurate statement - I wouldn't count on a police department "intepreter." I don't know what the law is about this, but at least in my case, I could have a friend with me who could catch the subtle (and not so subtle) mistakes to ensure that the statement I gave was accurate and not misinterpreted.

You don´t have to go to the police, you don´t have to make a statement, you don´t have to sign anything, you don´t have to swear or take an oath ...

@ jts - What exactly does the summons say regarding your obligation to turn up and possible consequences of your not doing so?

Let's say it like this then: IF you give a statement, then it ISwritten down, you DO have to swear to its accuracy and you DO have to sign it.

Whether the OP HAS to give a statement at all, this I don't know.

Not in Germany ...

On the other hand if this guy was chucking these things around nilly willy and one had hit a child in the face, then he deserves to get his arsch kicked

*apologies for any typos*

I was also told to bring my tshirt, which I do still have, mainly because it's not badly burnt, is a tiny hardly visable patch or two where the design got a bit melted but nothing else.
I speak German and have studied through German for the last year, but it's way too official for me to be able to make proper sense of. Also I thought I might add that the charge is "Gefährliche Körperverletzung", which giving the "injuries" i sustained, ie. next to none, is a bit OTT.
I was thinking of calling into the Irish Embassy tomorrow to see what they say about it, and actually have somebody explain what the f*ck all of this means, exactly what I am supposed to and expected to do etc.

You are being invited to visit the police station to give a statement. You are under no obligation to turn up or provide any written statement, however if the police believe they have sufficient additional evidence to take the case to court, you MIGHT be called to the hearing, which IS obligatory. If you are being called as the victim (which I suspect you are) and they have other witnesses who do give statements, then I think it's likely you will be called to the court. Probably better to give your side of the case now, especially if you think it's minor. I'm not sure it is - it could have been nasty. These bloody football fans deserve being taught a lesson. Shoot the lot of 'em. Flogging is too good.
If you really want to downplay the incident tell them you have lost/sold/washed your T-shirt. That's likely to be the only substantive piece of evidence.

this might not be because of your injuries but because of something more serious the guy did and your only one (of many?) witness(es). So just go there, tell your story and walk out, not big deal.

Yes, you do have to attend unless you have suffienct reason not to ("I don't wanna" just doesn't count). And you do have to keep them informed of your whereabouts, that's what your first quoted sentence is about; you may be interrogated in the UK as well. Judging from the other bits you are being interviewed as one of the injured parties, especially as you are requested to bring along your damaged item of clothing. As mentioned above, you may not be the one who sustained the worst damage but the police has to gather all available evidence to evaluate the extent of the injuries and damages.

Just go along for the experience. Its harmless for you. And if someone else was a victim you'll be helping them. If no one else was, and you don't press charges, miladdo walks.
I've been called as a witness a couple of times. Gives you a story to tell.

Are you certain about this, miwild? Can you quote a source? I was the victim of a crime, and this is what the detective told me, in no uncertain (or mistranslated) terms. So my experience is only anecdotal, and of course, the cop could have been lying to me, but I am curious what the law is specifically. Maybe Sarabyrd knows...

Every time I was summoned as a witness (in a private or professional context) I had to sign my testimony including the phrase about "I confirm that my testimony is a truthful rendition of the facts" ("Ich versichere, dass meine Aussage der Wahrheit entspricht"). When taking notes from the court files I saw that each witness' testimony contained the same phrase and the witness' signature. You can rest assured that this is standard procedure.

You can refuse testimony if you are related or engaged to the suspect or if you can implicate yourself or a close relative with any part of or all of your testimony. You can also be extremely forgetful.

However, you cannot be done for lying in the police interrogation as the police (and the DA, by the way) are not authorized to request sworn testimony. Criminal, civil and arbitration courts are, as well as e.g. government committees of investigation.
Die Staatsanwaltschaft oder die Polizei gehören nicht dazu, weil sie keine zur eidlichen Vernehmung zuständigen Stellen sind.