employee vs. freelancer in Berlin

German tax and social security issues are VERY complicated and, if done wrong, can have serious consequences for both employer and employee/freelancer - from high fines to jail!
So please do get a good tax consultant (employees/freelancers) and accountant/HR consultant (employer)!

To answer your direct questions:
- For your EUR18k/year-colleage the company must deduct the correct tax and social security amounts and send them to the relevant authorities, incl. the employer's co-payment. Altogether the employee has to pay around EUR5000/year and the employer another approx. EUR4000 (on top of the EUR18000) to public coffers.
- She has to get German (public or private) health insurance. The premiums for public insurance is included in the deducted amount above (private may vary). An international insurance is not accepted.
- Freelancers, too, will have to get German health insurance, but have to pay the "employer co-payment" from their own pocket. This means (for the public scheme) a monthly premium of EUR350-900, depending on overall income. (The private scheme charges by age and prior health condition, independent of income.) Freelancers are also income taxed, but do not need to contribute to social security (pension, unemployment).

Hello,

thank you for your reply. I agree that the best would be to use tax accountants/consultants,
and I am going to push this but until then, thanks for all the information

if there is anyone who can recommend me any reliable source of information, that would be highly appreciated.

Have a nice sunny day you all

Tax consultants in Germany have a legally sanctioned monopoly on tax advice - meaning nobody other than regustered Steuerberater are allowed to help you in such matters.
Their fees are also regulated, so no matter which one you choise it will cost the same (but the quality might vary).
But for the company you need an accountant. It is almost impossible (even for a native speaker) to do these things correctly without one. Many tax consultants are also accountants (or lawyers, which is another service you may need).