Like the title sais, at the very start of the game I recieve a mission to go to mikes bar, but it's empty, no npc's are there. Moreover some tables seem to be missing as well, as there are floating items around. I tried disabling/enabling v-sync, as I've read this solves some issues... It didnt help though :(
I also downloaded some game launcher that supposedly fixes some issues, and it did (no hopping people, or npcs moving away during talks), but it did not fix the mike's bar issue... Anyone knows how can this be handled?

Are you using the GOG version? That sounds like game corruption.

Do a full uninstall and reinstall.

ONLY launch the game with the Multi-Fixer launcher with the frame rate cap enabled and set to 60.

In your options menu, enable V-Sync and set the renderer to DX9.

Make sure you've followed the tutorial, and used the weapon computer to buy a weapon, then equip it from the armory FIRST before visiting Mike's.