Passed PSM I. Suggestions
It was great, I just passed PSM 1 with 93.8% score.
I can't tell that it was too hard, but it defenitely was not so easy as any online open assesments.
My way of study (all is free):
1) Scrum guide - read 4 times slowly, printed english paper with remarks! Each word is a key!
2) Open assesements - scrum open and product owner many times, you need to understand explanation of each question. Do it until you get 100% permanently.
3) Lapshin's suggestions and two scrum quizzes - http://mlapshin.com. You should stably getting 100%
4) Few times another available online test
5) Read one time scrum glossary
6) Read one time free scrum manual
7) Optionally read Nexus guide.
You need to understand the concept of Scrum. No need of mplaza paid tests. Sleep with scrum guide, start thinking using Scrum.
All the best!