Hello,
Unfortunately, VPNs are not all created equally. Due to the nature of how they work, you will get different levels of performance with different VPNs. If you are experiencing poor performance with one VPN, the best that we can recommend is to try another, different VPN or a different server on the same VPN. You might need to try multiple VPNs or multiple servers until you find one that works for you.
Hopefully you can find one that works!