So I am studying from an online site called Memrise but they seem to teach pretty straightforward stuff that you have to memorize in order to do them. Yeah I can ask and say things but I can notice that the verbs change when the context changes. Some examples:
The verb is usually
but in this context
かれはオフィスではたらいています。(He works in an office)
it transformed to a brand new version of the verb. Now I have memorized them both but if I wanted to say something else I'm drawing blanks.
And here's another example. I noticed a pattern between these next few but I'm still not sure how they transform:
どうしてそんなにかなしんでいるのですか？(Why are you so sad?)
correct me if I bolded too much. I'm not sure if the の particle is included in the verb here. The verb is usually かなしんでいます but here it transformed to the bolded part. This one totally confuses me. It's different from the next one because in addition to having the verb have いる at the end it also has the の particle. I know it's a possession particle but its use here is beyond me.
And here's the third example where it's really similar to what we saw in the second example:
わたしはおなかがすいているから、おこっています。(I'm hungry therefore I'm angry)
Right here I can tell that the verb is the bolded part and the から particle is used to show a reason meaning therefore in this context.
Do these transformations have a name? Something I can research online or from some text book. I see that the verbs have these forms but I can't group them in one category so I can research them. They seem quite random.
There are many others that baffle me like "ふん" -> "ぷん" in some sentences. But I guess that's it for now. I really want to go a bit deeper in the grammar so I can improvise in my free time by creating sentences in my mind and not mess them completely up.