Samurai / old school japanese issues

So I've been playing ghost of tsushima and goddamn do I feel like I got hit in the face by a 2×4 when they started speaking. Normally watching anime or TV shows I can understand a solid 80+% of what is being said but here it's like 40% at best. Is it almost a different language or do they use different helper verbs or something.

Any tips for better comprehension would be appriciated.