OK. It's easy.
Base Ian at the start is an ordinary guy, he is rather modest and a little shy. He lacks self-confidence and has severe PTSD after breaking up with Gillian. Which, quite likely, was his only partner. He is not as shy as Holly (there is a disaster in general), but there are problems with self-esteem.
Basic Lena. She is an open, moderately relaxed and confident girl in her sexuality. It is not a problem for her to pose naked for a photo shoot and she does not feel problems when she goes on a date with, for example, Robert or Ian. She had already done sexually depraved things with Axel and he was most likely not her only one. She does not suffer like Ian from a breakup, on the contrary, she wants to get away from this relationship and turn the page. But has problems with stalking from the ex.
The contrast between them is very strong. We can conclude that at the start, Ian is not from Lena's league.