If you do continue to learn Welsh via other methods (and I hope you do!), you need to be aware that there is a much greater difference than is the case in English between the colloquial language as spoken by native speakers in shops, social situations and in the workplace and the more formal language used in written media such as newspapers, articles in magazines, novels etc. SSiW teaches the colloquial form.
The difference is so great that many first language speakers, especially those who are middle aged or older and who therefore weren’t taught through the medium of Welsh at school, don’t read Welsh and are extremely reluctant to write it. This article sums it up nicely:
How many different varieties of Welsh are there?
It sounds as though you have your own established ways of learning a language and SSiW isn’t a good fit for you. That’s absolutely fine. The reason I persevered when I initially found it impossible was that I kept meeting people who had learned with SSiW and they all spoke much more confidently than the people I’d been in traditional classes with. I therefore experimented and found a way to use the challenges successfully. But if it’s not for you, then I hope you can find a course that suits you better. In case you weren’t aware, the traditional Welsh for Adults courses are currently being held online due to the pandemic. This opens them up to people anywhere in the world, so you could try Googling Welsh for Adults to see what’s available.