Why are my games jerky (PC)?

For 3 weeks I have had very stuttering in games like Fortnite or GTA 5, my PC is very good, so I wonder where these problems come from. I have a 1070 ti AERO and a Ryzen 5 2600x, 16 GB RAM, MSI B450M PRO-M2 MAX, AMD B450 motherboard. My RAM memory is not full (6gb of 16gb), 222GB SSD (155GB free), 1TB HDD (631GB free). The temperature of my graphics card is 65 degrees when gaming. And is 30% busy. The processor is 45% busy, I don't think that's too high. I have a 144hz monitor, and I play with a 1656x1090 resolution. I have a 25 ping, so I think it doesn't the graphics settings are all low, and I have VSync off, I have GSync on and I have very good FPS (200+). My PC is also connected with a LAN cable. I have all the drivers updated, Windows 10 as well, maybe it is GeForce Experience? I use it to make my clips etc. I hope that someone from you can help me.

Kind regards

Here are a few screenshots:

16GB RAM memory: .html

GPU idle: .html

CPU idle: .html

Three weeks fits the current situation very well, so I tend to 95% that it is due to the network. Depending on where you live and the number of users, problems may arise, because neither the maximum download speed nor the ping number says anything about a stable connection.