Been experiencing some FPS spikes and I want some advice please.

Hello, I've been playing this game for like 8 years, and lately, I don't now exactly which patch has caused this problem to start, I experience random fps drops into the game, I usually have like 100 - 98 - 90 frames per second. But sometimes It drops to 40, rarely to 10-15, it really impacts how I play and I don't know what's causing it.

I've been adding 8GB RAM memory, now I got 12 and I thought the problem may disappear, but no. I'll set up a picture with my specifications, In my opinion the problem is the CPU, and I'm planning on upgrading to an old i5 quad core, would that maybe solve my problem?

Please, any advice would help me, thank you summoners.