Gutenberg Blocks have strange magins

Hi!

Seems to be a dumb question but I couldn't find a solution.
https://edukids.netaction.de/elterncurriculum/krankheitsbild-was-ist-diabetes-mellitus/
All P elements and other Gutenberg Blocks have a margin:

.entry-content > *:not(.alignwide):not(.alignfull):not(.alignleft):not(.alignright):not(.is-style-wide), h1.entry-title {
width: calc(100% - 30px);
}

I don't know why this margin of 15px to each side even exists as the container (.one-container .site-content) already has its margin.

Current behaviour: P, H1, UL and everything has a second margin.

Desired behaviour: Everything in one line with the navbar and other content.