SIMS 4 BASE GAME UNABLE TO START - THE SIMS 4 IS ALREADY RUNNING

Hey! Upon installing the base game I got an error 12002 download microsoft.com/download. When I continued installation I got - warning 4154 - visual c++ and so on. After a forum search I've found that I was supposed to run two things in folder installer and folder vc. After doing that, I reinstalled it only to get a warning upon starting the game that says: Unable to start, the sims 4 is already running and a lot of numbers afterwards. I've checked the task manager to see if it's running somewhere and it's not. So if anyone can help me please, I'm really new to this. Thanks in advance!
p.s. i haven't installed anything else. am i allowed to download all the packs on torrent and then install one by one or do i have to download the games on torrent one by one aswell?

Re-boot your PC