Slow new tab page, impossibile to disable Pocket section

hi… since beta 58b8 (i think… or around that) my new tab started to be slow very often, with the rotating ball blocking all Firefox for about 2/5 seconds, probably loading the Pocket’s thumbnails.

it has become very annoying!
and i discover that the Pocket’s section can’t be disabled!

is it just me?
i wanted to try the release Firefox v57… but it seems that the user profile has changed in v58 and it’s better to not downgrade :frowning:
thank you for any tips and comment