Can I speed up progress?
Your progress speed is based on review accuracy. Levels generally contain two sets of characters where the second set is unlocked by “clearing” the first set. You “clear” a character by progressing it to SRS level 4 (correct reviews increase the level, incorrect reviews decrease it).
If you answered all your reviews perfectly and as soon as they came up, you’d be able to clear a set of characters in about 3.5 days, which means you’d be able to progress a level in about a week.
Mistakes in reviews can slow this down but are an essential part of the learning process. As long as you’re doing reviews when they come up, you’re doing everything exactly right. It may seem a little slow at first but that’s just how SRS works - and one of the reasons the first few levels are free forever 
When you have a few more words under your belt you’ll find that you have a lot more reviews coming up.
Why not use the real radical names/meanings?
也 is considered a radical called “mech” based on that it looks like the face of transformers.
As far as I know (and that is not very much) 也 is not a radical at all in most standards which makes things pretty confusing.
It’s true that we take some liberties with the naming and organisation of radicals, and even what constitutes a radical. The imaginative memory/mnemonic concept takes care of characters composed of already-learned components, but it’s not so easy to explain to someone just starting with Chinese how to remember the lowest-level components like ナ. In this case the origin of the form is “left hand”, but this knowledge is of limited use when it’s not applicable to modern usage and isn’t memorable as a left hand, visually. Instead we give it a nickname that matches its visual appearance and acts as a concrete image for inclusion in later stories.
As for 也, the correct meaning is taught immediately after the “mech” nickname - this is almost always the case throughout the course. The idea of a “mech” provides much better opportunities to create vivid and memorable stories for characters containing 也, compared to the actual meaning of “also”. In other words, by staying completely faithful to the correct meanings of these commonly-occurring character components, we would lose the efficacy of our teaching method.
In the earlier levels, there are a lot of examples of this but it becomes much less frequent later in the course.
How come some completely different characters and words have same meaning?
There is a great explanation for this on Chinese StackExchange.
tl;dr, this kind of pairing is extremely common in Chinese and probably evolved for the sake of clarity in the spoken word.