Not smooth picture

Hello everyone, I ran into a terrible problem that I can't solve for a very long time.
In general, I play fortnite using dx11 and I am faced with very strong lags or something, I don't even know what to call it. I have 400 fps in the game (creative mode) and even in it with such a number of fps it lags very much, as if I have about 30-40 fps. I was already completely desperate and I don't know what to do, I literally tried everything I could, dug into the BIOS and it didn't help either, here are my components:
Video card - RTX 2060 Palit StormX (no temperature problems)
CPU - Xeon e5 2687W (problem also not in the processor, because before that I was sitting on i3 (I just bought the video card first, so that afterwards I could buy the rest) and it also had microfreezes, but there were less fps, but the picture was the same laggy)
Motherboard - Klisre x79 (B75 chipset)
RAM - Atermiter ddr3 1600 (9-9-9-26)
PSU - Xilence Red Wings XN054 700W
Monitor - IIyama x2474HS (75 Hz, but the problem is not exactly in it, I tried another monitor history repeats)
The game is installed on ssd A-Data XPG (I can't say the name further, I just don't remember)
At first, I thought that the problem was in the RAM, changed the timings, frequency and absolutely nothing changed (except that microfreezes are 1600 less). Then I switched to the processor (I removed hypertrading, it became better in terms of FPS (in a real game, not 400, of course, about 180-200)), but there was no smoothness. Then I went to dig into the BIOS and changed the PCI Latency Timer settings (from 32 to 234 or something) and at first it made the game smoother, but then it failed again. Then I dug into all sorts of settings like the High Presicion Timer, which also did not bear any fruit. I switched to the software part, installed a new windows ltsc from the repack-me site, installed the 441.41 driver (I subsequently changed them, but changed little except the fps and settings), after windows tweaker I cleaned Windows from all shit and then just installed one fortnite , but that hasn't changed anything either. By the way, this smoothness problem is only related to fortnite (I really like it and I only want to play it). I came to this conclusion because on a clean Windows I did tests in other games, such as: rainbow six siege, osu !, path of exile. Everything in them was just wonderful, I did not notice any lags except in the path of exile (in this game, the optimization is quite lame). In fortnight, I also changed the renderer from 11 directx to 12 and nothing changed at all (only 11dx has minimal smoothness, but with microfreezes). I hope that at least someone will help me, because I am desperate and just don't know what to do because on a clean Windows I did tests in other games, such as: rainbow six siege, osu !, path of exile. Everything in them was just wonderful, I did not notice any lags except in the path of exile (in this game, the optimization is quite lame). In fortnight, I also changed the renderer from 11 directx to 12 and nothing changed at all (only 11dx has minimal smoothness, but with microfreezes). I hope that at least someone will help me, because I am desperate and just don't know what to do because on a clean Windows I did tests in other games, such as rainbow six siege, osu !, path of exile. Everything in them was just wonderful, I did not notice any lags except in the path of exile (in this game, the optimization is quite lame). In fortnight, I also changed the renderer from 11 directx to 12 and nothing changed at all (only 11dx has minimal smoothness, but with microfreezes). I hope that at least someone will help me, because I am desperate and just don't know what to do In fortnight, I also changed the renderer from 11 directx to 12 and nothing changed at all (only 11dx has minimal smoothness, but with microfreezes). I hope that at least someone will help me, because I am desperate and just don't know what to do In fortnight, I also changed the renderer from 11 directx to 12 and nothing changed at all (only 11dx has minimal smoothness, but with microfreezes). I hope that at least someone will help me, because I am desperate and just do not know what to do