Puzzles are very very unfair

I did a mate in 4 and still only got a +5 on my puzzle rating

It doesn't matter it's mate in 4. It is about puzzle's rating

Rating change depends on the member's puzzle rating versus the puzzle's rating

Try changing your puzzle Difficulty to Hard or Extra Hard

it's already extra hard

puzzles man puzzles

++

Решаю головоломки выше своего рейтинга и капает очков мало
Причём я думаю что мои нынешние головоломки далеко не самые сложные, а уже такой дисбаланс

Then that one was much lower rated that your current puzzle rating. You should get a good mix. I have don't many puzzles since the most recent change but my last full session I had (in the last 25 puzzles)
+5 : 4 puzzles (one missed and partial credit)
+8 - 10 : 5 puzzles
+11 - +15 : 9