This is one of MANY tricky plural oddities in English. We refer to homework as if it were all one “task” to be done. Every example of a noun ending in “-work” tends also to follow this pattern - yardwork, housework, teamwork, even work! I hope that helps and makes sense! Please let me know if it does not!

Even though homework is probably referring to more than one assignment, the last two sentences can be written like: "it's not easy to do it. I want to finish it soon." I would personally write both sentences as one like this: "It's not easy to do it, so I want to finish it soon." You could also use 'but' in place of 'so' in this context. I hope that this helps!