UI Autocomplete onfocus/onclick = slow

UI Autocomplete onfocus/onclick = slow

Hello, this is my first post here, I hope it is the correct place :-)

I have 2 websites; on website A a complex form F with 70 inputs with autocomplete; here it works fine.
On website B, same form F, but several other jQuery plugins.

On website B, when I click on any input (with autocomplete), it gets the focus only after 1 second or more.
On some slow computers / smartphones, users need 5 seconds... and think the website doesn't work.

How can I find the problem, the conflict between plugins, the function that slows down everything?
Is there a way to simply desactivate every or some plugins on this particular page?

you can find the F form on website A:

Website B cannot be opened without login.