[Membership 2 Pro] 504 Gateway Time-out & Slow Down Plugin's Link

Hello ,
I am setup the plugin in staging website before I will use on my client site.
When I try to create membership it is take time then gave me 504 Gateway Time-out , When I back to dashboard I am seeing the membership on the list .

When I try to configure it is slow sometimes and other times give me same error.

I am givining you the access

Thank You