1st manga: It's about a brother who has to buy a bikini for his sister. The woman at the shop looks like his sister and asks for the bikini size. Then they have sex.
2nd: It's about a schoolgirl who wants to make the nr1 in school have bad grades by having sex with him. It's set in the library and the girl is blonde.
3rd: It's a yuri h-manga. It’s about two colleagues who use a double dildo. They know each other from school. One is transfered to the place where the other one is working already. Her husband is never there so they have sex at her home. They are in the bathtub in the beginning.
4th: It's about about a calligraphy teacher showing a student how to ‘use his brush’ but it’s not the one by Meme50 which is called ‘servant’.
It would be nice if anyone could identify some of these mangas because I already searched all the sites and googled so much.