ALL request to web api became slow on IIS [closed]

I have fine working web api app, IIS hosted, web api 2.0, win server 2012r2, IIS 8.5. After moving this application to IIS 10 (Win server 2019), ALL request became slower approximately 3-5 seconds. Again, all requests, not first. App pool is "Always running" E.G. /token request runs 3.5 seconds instead of 30 ms on old server. And all requests runs the same manner.

What can be the reason?