After updating WP and plugins, the site became very slow. Could you check?
I would agree that you have a lot of plugins, in my test your large images slow down the site
but the biggest concern is that your web server waits over 3 seconds to start sending the webpage, this is very slow.
your First Byte should be more like half a second, like this:
I disabled some plugins and contacted the webhotel. I have no idea how the get this better….
Unfortunately, there is nothing you can do to correct the First Byte time, this is a server issue.
Some “budget” web hosts will place too many customers on each server, slowing everyone down.
I’m not knocking your host it’s just how web hosts can offer low prices, if you can afford to pay more for your hosting try researching “fastest web host” for your country most review sites will show the host speed for their tests.
Then most hosts will let you test for 30 days so you can compare.
If you find one you like, most hosts will have coupons for 60% to 80% off for your first contract, the trick is to get the longest contract time, such as 2-3 years.
You might end up with a 3 year fast webhost for the cost of 1 year at the regular price.
Either way, it can’t hurt to test a different webhost for free for 30 days, just my opinion.