I want to post a adsense (responsive) add after first post

Hi,

Could you help me edit the content/index page to show a (responsive) add on the homepage. OR if this is hard a header (responsive may bring a square add).

Or if its possible, for instance a header when there’s enough room and no ad when there is no room for it (mobile). I tried adding it before the endwhile on the index, but i am no php expert. I truly dont understand php, only a little html :).

If you could help me i would be very happy. Greetings Adriaan
https://just-autism.com