how to increase website speed

If the slowness is due to the image loading I advise you to use a CDN, I use imgix that has 3 months free and loads the images in an absurdly fast way. But you can use the Amazon cloudfront or the jetpack CND itself.
If the problem is with the scripts or with the css better they compact them intelligently since some can cause instability in your site when minified. It would be good to use clodflare or others