the time taken for clearing customs
& immigration depends on several factors - how many planes come at the same time and from where are the passengers and how many of them show up for how many open booths.
As a German you need no visa if flying into the USA, but you will have to sign in to the ESTA site before travelling. Go to https://esta.cbp.dhs.gov/esta/applic...execution=e1s1 to complete that formality.
If you want to sail to the USA (i.e. Puerto Rico
, USVI or the mainland) you will need at least a tourist visa and for that you have to complete the forms and then travel to Berlin for an interview.
If you only are transiting the USA for St. Maarten then entry will be no issue. If you are flying from Germany
to Puerto Rico
directly and don't arrive at the same time as other flights, clearance should be quite fast and no more than one hour.
If you wish, you can PM me in German if you have questions.