Some advice (some of it obvious if you've dont it before and not specific for Germany but maybe it's useful):

Have a profile on Linkedin and Xing, upload to sites like freelance.de and maybe to a bunch of agencies. Be ready to send a profile, listing as many projects as possible, i.e. different roles in a company could be separate projects. Make sure all relevant search terms (languages, frameworks, tools) appear for each project even if repetitive. English-only is ok in many places, German-speaking projects can be a little better though.

It's all through intermediaries, which means you can (and should) negotiate rates hard without worrying about burning bridges. No call with a recruiter that didn't go pleasantly ever led to anything so if it feels weird just hang up. Expect to be placed 3-6 months min, 2 years max in a project. Research a little on "Scheinselbständigkeit" but it's not a huge issue these days. If you want 100% remote it should be possible.

Good luck and welcome to Germany :-)