I bought a 144hz monitor yesterday, but when I was trying to enter half life, I saw that it returned to 60hz and the game was worse than 60hz, what should I do?

I've had this issue before. Try changing your resolution to something different and then back to your preferred resolution, I think this fixed it for me.

i still have the same problem... but I don't have this problem in windowed mode

I suspect AMD FreeSync

problem solved. I had to type -refresh 144 in startup options