Thanks for posting your feature request in English.
I am not trying to nitpick, but I created the "PLEASE READ BEFORE POSTING*" post to keep the forum organized and me not having to ask the same questions all them time ("What app version are you on?", "What operating are you using the app on?"etc). I created placeholders in the template when creating a new post to fill out, to make this easier for users.
Multiple feature requests in a single thread (in your case "smaller QR code" + "font in main part is too small" + "different placement of QR code") make it hard to have a focused discussion. Thanks for understanding!
Let's focus on your first request: the QR code size. What QR code option did you select in the app settings and how small should it be in your opinion? Half the size?