I feel like a lot of their arguments must be lost in translation, but I also believe they both have some sort of an agenda in that relationship.
Teo seems like he's just plain immature and uncaring just in the way he acts and talks. But I also think that Riri can be quite manipulative.
I remember in the week they joined, she started talking about marriage which seemed to take him by surprise. His stance was to wait a bit because of money shortage, and her whole angle revolved around the fact that he'd have to marry her now otherwise she'd be forced to go back to her country (Kyrgyzstan? can't recall) and that means he doesn't love her. That discussion came out of the blue and felt just weird (just chilling in bed and she started crying and threw that out). Also she seems to always find a brand new reason to fight him over, with some of new probably being legit, and pushes the buttons until he becomes submissive enough to do whatever she wants after.
Then there's also him being quite the idiot. During one of the holiday parties they held, he very awkwardly tried to lead one of the guest girls on to the point. She immediately saw this as a red flag and bounced off the apartment soon after.
TL;DR: Red flags & not much love between these two, imo.