Brand and characteristics would be helpful.

Thats a tough question to answer without any info on what you want to fix! Duro is great as is apoxie sculpt. Give us more information or pics even and we can help!!

I am currently working on german mountain soldier figure, but shoes are too small, so I want to model a correct size shoes.
My camera is currently out of batery power, so I need to recharge them if you need the picture. It will take some time.

Also there are some things on my other figures that should not be there, like holes, damages, scratches... If you can recommend something to do the job filling those holes, and not folling of, if i need to carve it with knife a little.

Maybe this thread will help you for fixing holes and minor flaws:
http://www.planetfigure.com/threads/pin-holes-in-resin-casting.45860/

Nearly any of the epoxy modelling compounds would be suitable Dominik. Most of the main options are listed in this recent thread:
http://www.planetfigure.com/threads/which-modelling-putty.47349/

There's no best here, like with just about anything personal preferences can play a big part in what someone uses. Plus price and availability need to be factored in.

Einion