Taxes for self employed

I plan to be teaching English online, setting my own hours, and would be getting paid a lump sum into my PayPal at the end of each week. How would this effect me when I do my taxes because I read it's important to keep track of each client and all sorts of detailed information? The platform i use simply pays the lump sum into my PayPal each week depending on how many hours I work making it impossible to gather client information for invoices like I read about in other posts.

You better engage an accountant and tax consultant for these topics, which are extremely complicated in Germany. Doing it wrongly is a criminal offense- and they do check!
I only know that you will have to issue a proper bill (that correctly indicates the "MWSt" or GST, which you have to deduct and send to the tax authority) before payment and that there are corporate taxes to be paid on the profit, as well as income tax on the portion of the profit that you keep for yourself.
I do not tink the setup you describe will work at all here.