Yeah, I see tons of notifications up at top.
That is definitely a way to bog down a phone.
If it is an app that you use a lot, ditch the notifications on that one.
You will get the messages when you open the app anyway.
If it is an app that you don't use much, then ditch the notifications because you are not using the app much anyway.
Back to the Express VPN thing- using a VPN will drastically slow down online performance (when compared to not using a VPN at all).
Try using a firewall instead, because doing that can actually speed up performance in some cases.
https://noroot-firewall.en.uptodown.com/android
Also, any time you have filled up more than 75%-80% of the device's internal memory you risk bogging it down.
This is due to apps expanding and contracting as they are being used.
It is best to try to maintain internal memory at no more than 70%.