csgo smoothness, hitreg and mouse problem

Hey guys, i want to ask what in your opinion can cause this problems. I will describe it with csgo but it occurs in other games too. Every cs run it works different. Mouse is responsive only if there is few people, while playing some polish dm its stuttery and not smooth but playable and if there is more than few people its just less smooth and laggy. On competetive only few minutes of first game are smooth and next games are stuttery and slow with broken mouse and hitregs, it just feels like 20hz so i cant play, temperatures are normal. I have 75hz so i tried 150fps like twice as refresh rate and on polish dm it was slower but playable and on competetive also it was less smooth but hitregs were fixed like it was easy to see. Later i tried those fps again but on warmup dm and it feels like normal 240fps, so how it feels better with more people than competetive? Basically in small areas with few people it feels smooth but with the same fps but more people or if people are close it stutters. I was playing with bots with unplugged ethernet cable and mouse was floaty and shooting feels like 20hz but what i noticed is that if there are internet problems like loss mouse is more responsive. So guys how on competetive only few minutes it works normal and then it just feels like 20hz, also if i go to inventory or settings half of fps drops. As i said, in other games like fortnite it was the same, fps were playable but i basically wasnt able to play. Im using ethernet สล็อตจ่ายจริงไม่มีขั้นต่ำ

i5 9400f, 1050ti, 16gb ram, 75hz