The masdar get used when you talks about the origin of the thing, when we use the verb, we can use the masdar instead. for ex. -Mohammed trains alot (محمد يتمرن كثيرا) . or -Mohammed is doing alot of trainings (محمد يقوم بالكثير من التمارين) . We can't say "Mohammed trainings alot" because it must be a verb not masdar.

well, you can think of the masdar as a noun. you can use it only when you need to talk about the action itself. أحب لعب كره القدم here I was talking about me loving the (playing) action itself which is different from هو يلعب كره القدم and also different from هو لعب كره القدم بالأمس which is the past form....but it looks like the Masdar. but with different "Tashkeel"