No you don't need a professional. I clean mine with a mild ph neutral soap like ivory dish detergent. Rinse and dry. Don't clean with a sopping wet rag. Just a well rung out rag. Let air dry. Then condition with a good leather conditioner. I personally like to use Leather Honey. I get it from Amazon. Apply the conditioner and leave it sit overnight. If the leather is dry you might have to do this a couple times until the leather is fully hydrated. When the conditioner doesn't disappear into the leather then it it fully hydrated. Then just buff with a dry rag to remove any excess conditioner.

what about against potential bedbugs etc? do i need to scrape the leather to find "residues"? i dont need any sanitizing agent either? I dont think the owner is a slob or anything but you never know? it is sharp discount of ~2k but it is 3 years old but then again i hear Ethan allen leather couches can last a little bit...

I never had to deal with bed bugs and hope i never have to. Maybe look for evidence of the little critters. Bed bugs have nothing to do with someone being a slob or not. They can hitch a ride into the cleanest of homes.

Leather is only as good as the care it gets. Assuming the owner has kept it up properly, then, good buy. If not, the leather has started to dry out, especially in a home where there is no HVAC.

I’d take all the cushions off, vacuum everything, especially the under side. Then follow functionthenlook's advice.

Throw pillows on leather are a pain in the neck. I’d recommend lumbar pillows with a rough fabric, like kilim.

Hope this works…love the one long pillow.

https://www.etsy.com/listing/735946199/long-carpet-pillow-12x48-inches-turkish?gpla=1&gao=1&&utm_source=google&utm_medium=cpc&utm_campaign=shopping_us_ts1-a-home_and_living-home_decor-decorative_pillows&utm_custom1=kenshoo_clickid&utm_content=go_920092452_47675451764_218669179812_pla-302796601582_c__735946199&utm_custom2=920092452&gclid=Cj0KCQjwwOz6BRCgARIsAKEG4FUMRGEgSxuwClckPDEf0pKY9-h1CkO5vTzCJEuFNP6tEAL_f-R1EWMaAhvKEALw_wcB

Good old saddle soap or castile soap. With saddle soap, it only needs a light rinse, then a buffing will make it shine. I have been in the horse field all my life, and it's the best cleaner hands down.