Michael gave some really important advice: "stick with it".
I study languages and linguistics at uni. One of my courses is "Learning and teaching a foreign language". There are always difficulties with adults acquiring other languages. Linguists have been developing methodologies for hundreds of years, with varied results. But, there is still no ONE best practice.
Japanese is considered one of the most difficult languages to learn. I find their phonetic system quite straight forward. The writing system, though, is time-consuming. My katakana is still shocking.
There are "how-to" people out there who have some advice that is worth considering if you feel your progress is not advancing rapidly enough. Have a look at this video https://youtu.be/_IOZbJ7PCPk and tell me what you think. The kind of learning that this man suggests I believe would be very intense, and I think many of us just lead lives too busy to fully immerse ourselves as we'd wish.
Even for speakers of native languages, it takes between ten and twenty years to achieve "discourse competence" - and that is in our own language, the very language people are speaking all around us. Of course it's going to be a little tough for a Belgian or an Australian to learn Japanese!
I'd also like to mention "foreign language classroom anxiety". It is a real, common thing that many of us have to cope with and causes many people to give up.
And that is what I'd like to encourage you NOT to do: give up. Learning other languages isn't a test of our intelligence, it's a test of our fortitude. If you keep on with it, I can guarantee you will know more next week than you do this week.
Buena suerte