www.thinkwithgoogle.com says my website is slow (3.9sec loading speed, yea it's truly slow...). To increase loading speed it tells me to use "next-gen" format for my pictures, e.g. jpeg2000 instead of jpg.
All pictures (except logo) on my website are jpg. If I try to convert them into jpeg2000, the are not getting smaller in size, they are getting MUCH BIGGER.
E.g. one picture had 39kb of size in .jpg, after converting it to jpeg2000 the exact same thing had 261kb. So why to use jpeg2000 then?