New update has slowed down everything why???

If it were that simple, the new update would have included a fix for such a problem.

The real "fix" is a thoughtful analysis of the exact problems your particular Mac is experiencing.

Here is one place to start:

Runaway applications can shorten battery runtime, affect performance, and increase heat and fan activity - Apple Support

.

Repair the drive

Do a safe boot

Post output from Etrecheck

Might be you are running something that broke with the update, very possible and not uncommon..

But you should be in a MacBook Pro forum area