Frustration

Hi Alexander, it very much depends on your goals.  Are you looking to increase your knowledge and understanding or just go for a certificate.  If the former, I would suggest attending a training class to really help you understand Professional Scrum and remove many myths that you may have picked up through the years.  I also suggest a great new book Mastering Professional Scrum.

I do not like doing the practice test on scrum.org due to the answers are ambiguous or not correct. Just confuses me more.

I never noticed this. Devil is in the details sometimes, pay attention to words like "must" and "should". I think the tests on scrum.org are very mature, the SM practice track should not contain wrong or ambiguous answers. If do feel like this, please explain / ask on this forum

I do not like doing the practice test on scrum.org due to the answers are ambiguous or not correct. Just confuses me more.

All due respect, I'd argue that the only place you should be doing practice tests is scrum.org because it's the only place where the answers are CORRECT. Have you considered that you're having so much trouble passing because you're going to external sources? I'm honestly trying to help with that question and don't mean any offence with that.

Is English your first language? If not, that could also be an issue. Like Xander called out, the devil is in the details with questions asking "what MUST be done...." etc etc and that's where it trips people up; primarily non-native English speakers. 

I have memorized the answers.

When I was preparing for the PSM1, I got to the point of having all of the correct answers on the practice tests memorized but I went 1 step further; I focused on the incorrect answers. I paid close attention to the answers that were wrong and made sure I knew WHY they were wrong. So much emphasis is placed on knowing "the right answers" but far too little emphasis is placed on knowing WHY other options are incorrect. I highly encourage you to go through the practice exams (even the external ones if you really have to) and focus on the incorrect answers. Shoot for scoring an absolute 0 but make sure you know without a doubt why the answers are not right. The twist though, pay close attention to the answers that are ALMOST correct make sure you know why it is not absolutely correct.

If you are struggling with English, please use the Google Translate Plugin. Not perfect, but very good.  Learn more about how here.

Alexander, if you happen to live in/near a large city, there's a good chance you have meetup groups (or similar) for people who are interested in Scrum or agility.

They can be a good place to go to develop your understanding of Scrum. Maybe you can take the opportunities to discuss difficult topics and challenge your own views/assumptions.

If possible, also try to understand whether the people you speak to have Scrum.org certification or not.

This isn't to say that people with Scrum.org certification are the only ones worth listening to; but they should understand how the exams work, and be able to share advice that's relevant to your context.