Zuico Zoom or Prime?

Hello there!

I'm fairly new to photography, and I recently acquired an Olympus OM-10 as my first-ever film camera. It came with a 75-150 f/4 Zuiko lens.

It's great, and for portraits and whatnot, however, I would like to have a lens for everyday use (something like travel as well)

My local camera shop has a 35-70 f3.6 for sale for around 90€, which is a great lens from what I heard. On the other hand, on ebay you can find a 50mm f1.8 for around the same price (shipping included)

I'm torn apart. On one hand, you have versatility, with 35 and 50mm; on the other hand, the 50mm is smaller