Hello there!
So a while ago i got a second hand nokia n900 with messed up maemo, it turns out not only was the maemo messed up but the micro USB port too! So i took it to a repaitshop and from there they told me they cant fix it! So i desidet to take a look inside and as you people can see on the photo there is teribly soldered port with a strange wire going out! (See photo for more details)
So my question is: what is that wire doing there and its purpose and if i can somehow fix the port!
P.s. is more photos are needed I'll upload more!
Image: https://ibb.co/kDPot5

there are several long threads on this topic. It looks like a patch line to the paired data in or out pad under the battery. I remember people adding a dip switch to short them for dumb chargers and inductive chargers.
try this one:
talk.maemo.org/showthread.php?t=37107
Anyways I would suspect either a shop repair or it is a Chinese 'new' refurbished N900 with a new plastic case.

It means they already killed the original traces for the port. The 'strange' wire is one of the data lines for USB. That's an alternative location for it (a bit debatable as apparently some of the electronic protection is not available at that point [fuse if i remember])

you're in bit of a problem - need to find someone really good at SMD soldering to do it for you. They'll most likely need to use two 'strange' cables

Good luck

So any chance of me repairing it with my noobish soldering scills and a normal soldering iron?

SMD soldering is not exactly easy, and the location of the port on N900 isn't very convenient either. For what it's worth, I fixed both my N900 and had never done any SMD soldering before.

Only you know your skills with a soldering iron. If you honestly think you can do it yourself, remember to get lots of flux. You will need it.

What Sicelo said... and a good magnifying system, I like 15x for this size, and bright light I like both a white LED or two close up with some shrink rube on the sides bent to aim at your work area as well as a bright desk lamp with a circular tube on an adjustable arm mount. When I fixed several N900 USB ports I also tried scraping a bit extra so that the adhesion area for the solder blob would be larger. My experience is to suggest you tin both the connections on a new clean port(buy several spares for practice and in case you clog one with solder) and also tin the pads to clean and prep them, I like to clean up the old flux and gunk with clean ethanol or methanol alcohol with minimal water.
Then clamp the port to the board solder down the anchoring pads on both sides, then finally touch each leg with the iron or use a hot air gun, inspect your solder joints with microscope and bright light. In your case I suggest getting some magnet wire and attaching the one data jumper wire before you attach the port, then once it is attached and other pins test good attach the data port jumper. Dont forget to tin about 1mm on both ends of the magnet wire before you begin and then attach the jumpers to your USB ports.

Can i maybe get some more in deph tutorial because i dont know how to connect it and i dont know what to do "

But is there a way i can use the old port??

Not sure what to say, why work with a gunky dirty and currently non-fnctional used part? Easy eliminate a possible failed part, a USB port is probably under $1 if you buy a bunch on tape, but I am seeing around $5 for one on a quick ebay search try: microusb port and sm and find one with the right anchor pad tabs to match that of a N900.
learn how to solder, very good video https://www.youtube.com/watch?v=jGZKsuaJlpo
and read this thread
http://talk.maemo.org/showthread.php?t=75920
most people won't try this fix, maybe you will and will suceed. WHat do you have t loose? A blister on your finger?
FWIW I have done the N900 USB fix maybe three times with only a roll of 0.7mm 50/50 electronic rosin flux solder a desk lamp a 15x eye loupe and a terrible cheap Frankenstein soldering iron made form the heat coil of a 220v iron and a slightly better tip but still junk 110v US soldering iron.