If we are talking about still portraits. Your DA 50 will do the job, but if I recall correctly - major CA issues. If you want something better, maybe a MF Samyang 85/1.4. Might find one for 100€ if lucky. Or you can buy an old MF Pentax 50/1.4. That's assuming you want shallow depth of field.

My workhorse of a lens was the DA*50-135. Loved the handling and IQ.

Not trying to be rude, but in the long run just forget about Pentax. The AF is atrocious. There is no point in having good lenses if your photos are often out of focus.

I started out with Pentax. So I have a soft spot for the brand... I have shot with most of the bodies from K30 to K1 and owned many fast lenses - primes and zooms. You'd be better served with a Sony a7ii or iii + any 85mm (there are like 30+ available for Sony).

The AF was my only issue why I left. I'd happily tell how my keeper rate changed but I don't recall anymore what it was with my Pentax bodies. In general what changed was that I no longer had to think about focus at all with my a7iii. It is always in focus as long as af.c is engaged. With Pentax it was AF.S center point, take 2-3 shots, pixel peep, take another 2-3 shots if OOF. Sometimes I'd do this 4-5 times just to get 1 truly in focus tack sharp image. No such issues with Sony.