Hi Wahnfried, I totally agree with Carol on Orient. Orient at the old Club O is generally our go to beach. We usually pack a cooler with drinks and bring sandwiches from Zee Best or Le Sucriere, but the food at the Perch is good and the drinks are reasonable at happy hour from 1:30 to 2:30 each day.

Here are some additional ideas.

Cupecoy can be just a bit of a challenge depending on whether or not there is sand covering the rock on the main beach. There are several other beaches there which require a bit of a climb up / down stairs if that is any problem. Dany runs the beach bar and can let you know.

Baie Rouge can be c/o if your walk a bit to the left as you enter. The water can be rough with undertoe depending on the conditions.

Many people like Happy Bay which is c/o but it's a hike to get there by either of two routes.
From Friars Bay walk north on the path over the hill.
From the road next to the basketball courts before you get to Grand Case (headed from Marigot). Park on the side of the road near the gate and follow the path south to the beach.
Either way, at Happy Bay, it's best to go with someone that's been there before.

Have fun.