Hi. I have game installed via GOG client -> patch 1.175. In KZR doesn't work restock in Gun Shop. I tried wait 7 days on the map then in hotel and nothing.

This is my first playthrough, so Im no expert, but dont rely too much on the merchants for your gun upgrades. The ones in my game rarely upgraded either, even after 10 days. Almost every good gun I find is through killing enemies. My best rifle, shotgun, and automatic weapon have been looted from the cold dead hands of enemies.

The normal restock takes 3 days.
Try to rest in front of the shop NPC for 3 days and check if that helps.

But the best shop NPCs in the whole game will still be the caravan traders in Peregon, as they're also the best for selling items you farmed by killing random world encounters: it's pure RNG, but they have almost all the weapons, armor and misc items in their vendor inventory.