Wifi working fine with VPN on phone but not without it. Please help!

[shadowlove]

Hi,
I am facing this weird issue from last few weeks, my home wifi is slow on my phone (Moto G 1) but fine on other devices. But when I connect through VPN app, it runs perfectly. Websites never loads completely when I don't use VPN, the blue loading bar of google chrome app never completes, even if I stay on a website for 5 minutes. Whereas speedtest always shows me the right speed.

I've tried everything from resetting the phone to contacting the ISP. Even the ISP couldn't provide me the solution. This VPN thing too was discovered by me, while searching for solutions of this problem.

I guess, the issue is not in the phone because other wifi networks works fine on it. And if it was about the router then it had also affected the other connected devices, but that's not happening. Iphone, Moto G3 and a laptop, everything worked fine on same wifi connection (without VPN).
I just can't use VPN everytime to use my wifi, with no options left I'll have to deactivate my internet subscribtion.

I hope experts on the forum will help me with this issue.

Thanks for your time.