qbitorrent download speed is low and don't reach my max speed

[simohub-sudo]

Please provide the following information

qBittorrent version and Operating System

(V4.3.1 WIN 10 20H2 64bit)

What is the problem

(it's been a week now since qbitorrent download speed became low and don't reach my full speed even though there are tens of seeders with so few to zero peers, this does not happens all the time but most of the time, a file would start downloading at max speed then afterwords it slows down to either quarter the speed or to even kb/s or even stop downloading
what is weird is that when i delete the file from the client and try to reopen it again and then it resumes the download but the speed would drop eventually, so i have to always delete files from client and reopen them so i can faster the download but this solution doesn't work always, i thought the problem was me installing malwarebytes but now i'm pretty sure it was not the cause after number of uninstalling and rebooting, and i always run speedtests, thank you.)