Ok, we solved this problem by creating a new block.
1. We created a new block (simplehtml) with the guide: https://docs.moodle.org/dev/Blocks
2. We added to the block_simplehtml.php some code in the public function get_content to generate the desired links. Each link looks similar to this:
"$this->content->text .= "<a href='$myBasePath/group/index.php?id=$myCourseId'>Groups</a><br>";"
3. We added the new block to all new courses by adding "$CFG->defaultblocks...." to the config.php
This way now we have a new block in each course with some quicklinks for the trainers.
But now we encounter the next problem. ;)
We want to display the new course block in all course pages, not only the main pages. Right now the block appears only in the course main pages. I can change that in each course... but i need it to be displayed in all course pages by default.
Any ideas? Is there any posibility to add this setting into the block code?