I wonder how hard and expensive is it to improve my soldering skills from basic use of soldering iron at the bottom (solder some wires in the way the connection won't break) to be able to replace the microUSB socket at the top plate.  

I definitely need some more advanced equipment  
But how much and which one.

@yura ah, the soviet soldering irons

i think mine is just a bit newer than yours but still probably from the 80s

@lina my is relatively new (from 2017-2020 I guess) but was made by soviet standards AFAIK, yeah.
@yura@udongein.xyz @lina how does the wood not burn? ​​
@witix @lina I think it will if I keep it on for a few hours (if nothing else burns before).
But the heating element is on the top part and there're holes close to the wood. I guess they help with not letting heat quickly reach the wood.