Googles "Pagespeed Insights" gives my page a low score because of Gumlet

Good afternoon,
I have run a page-speed analysis with Google’s popular Pagespeed Insights tool (
My site is
Google give the site a C- rating on Mobile in particular, seemingly because the images delivered by Gumlet are slowing down loading times.
Can anyone share ideas about how to improve response/loading times?
Than you!