admin customisations for restricted user

Hello. i need some modifications to admin dashboard, is that possible to do it by myself? (please give some examples and direction)
1) user with limited rights, user cannot modify anything on the site except its own info.
2) hide reports link for that group of users
3) display custom link for that group, for example "menuitem1" or customized Widget (what would be easiest)
3.1) display content from file, different for each user. user must not see other's users content.
something like "if username=$1 include /somepath/$1.file"
$1.file is html or .md with its own twig template (what would be easiest)