After a lot of fiddle - still need help

Hi,
sorry for the unspecific title but it's a bit more than one challenge I face.
With the help of this forum and Chrome's element inspection I was able to do most I wanted. I'm a pseudo CIO but not a CSS and JS coder.

Maybe a additonal info: to improve the speed of my site I installed W3 Cache and subscribed for the free version of cloudfare. Through this forum I found Async JS and css. Minification through cloudfare so far didn't work. This info as it may not be the theme but the configuration I have:

1. I have some errors
Uncaught ReferenceError: jQuery is not defined
jquery-migrate.min.js?ver=1.2.1:2
Uncaught ReferenceError: jQuery is not defined smooth-menu.js:21
Uncaught TypeError: undefined is not a function
javascript.js:252 Uncaught TypeError: undefined is not a function

2. My site doesn't work at all on tablets/smartphones. It would randomly load a different theme (which all I have deleted now)

3. It won't show the featured images on the front page, only when I login to WP as admin I can see them else I see white spaces.

For the handheld devices is it recommended to use the jetpack mobile them ?

thanks for any hint

EDIT: Disregard cloudflare, just deactivated and will setup dropbox