Hey there @Florian40788 - great question! Thanks for posting this topic. =) 

Firstly, check out our New User Guide - it’ll def prove helpful as you get used to the platform!

At this time there is no way to make payment collection optional on an event type. If you implement payment collection via PayPal it will be required of all invitees booking that specific event type. However, there is a workaround that is perfect for this situation - and I can walk you through it (yay!). 

Firstly, you’ll want to clone your event type. You can do this by clicking the “gear” icon in the top right on your event type and clicking “clone.” On the cloned event, remove the payment collection option, and include in the event type description that cash will be collected at the event (or whatever you would like to say). Read more below: 

Now, you have two options: leave both event types on your public booking page and allow invitees to choose the one that suits them (in this case, include payment type in the event type titles, i.e. “Event Type Name: Pay via PayPal” and “Event Type Name: Pay via Cash.” Or, make both events secret and then use routing to send invitees to the correct event type.

Routing forms let you request information such as industry, company size, specific interests, etc. from website visitors and automatically direct them to a specific scheduling or web page based on their responses. It's great for screening and qualifying sales leads on a website or matching clients or students to the booking page of the right subject-matter expert based on their interests, program, or other criteria. You can read more about setting up routing forms, here!

In your case you would use routing to send invitees to either your PayPal or Cash event by asking a routing question like, “Which method of payment will you be using to book today?” (Answers to choose from would be “PayPal” and “Cash.”) Then, the invitee is sent to the booking page of the event type that makes sense - no choosing necessary! Read more below: 

I hope this helps! Let me know if you run into any problems.