"Looks like this project is already opened"

Questions & Answers
1

everytime i try to open my project i get this message despite the project not being opened

2

Force quit all unity processes in task manager

3

If Unity is not running, delete Temp/UnityLockfile from your Unity Project directory

4

If you have windows you can open task manager using key shortcut: Ctrl + Shift + Escape - and kill unity editor process which wasn’t shown

5

But what if I want to open a second instance?