No worries at all

.
Regarding Erast, he has some very limited but interesting interactions. He is one of the kind ones. He is not really interested in a sexual relationship, or at least I haven't found how to make him interested in one.... but if you talk to him he can become friendly with you to the point of protecting you in school from the gopniks when they try to force you into the bathrooms for a bit of "fun" . You can talk to him at the dance party on the weekends or during school breaks and little by little increase his opinion of you that way.
Regarding Grigory, I haven't done his content in a while, but as far as I remember it was just a matter of walking around those fields until you see him in the field, approach him, talk to him and then hug or whatever you want. After that he will randomly show up at the barn. There isn't much story there either, you can't make him your boyfriend as far as I know, but you can have sex with him, he says he has had a crush on you for a very long time, and if I remember correctly you can even become pregnant.