"I did not swim much last month."
I know I've done several of this style of sentence without the は particle following the "time" (先月 here), but it was marked wrong this time. Is there a reason it's considered incorrect to leave it out in this case, or is this just an inconsistency? And if both ways are acceptable, which is more often used (with or without は)? Thank you!
My impression/recollection is that the は particle after a relative time expression such as 先月 is optional and often left out in conversation (but I'm not an expert so correct me if I'm wrong). However, I've learned to please the owl by putting it in the は particle if Duolingo complains. In this sentence, I left out は and it was accepted.
This deals with mostly the に particle and time expressions but I still found it helpful and printed it out. https://8020japanese.com/time-expressions/
あまり has a negative attitude. When you are trying to make a negative sentence with much in it, you might wanna put あまり. It can be used for number. However, there's another usage for あまり. It is 'not really'. あんまり is a word derived from あまり and has a stronger accent. For example, 'We don't see fishes that much this year' can be translated to, 今年は魚があまり見えないんだ and for 'not really', 'I don't really have interests in it' can be translated to, それにあまり興味ないんです。 沢山（たくさん） means simply 'much/many/a lot of' and it is positive / neutral. For example, 'There are a lot of electronics here' can be translated to こっちには電子機器が沢山あります
you cannot disjoint the verb like that, you can see 泳ぎませんでした as one full verb inflection, even though is obviously using auxiliaries to transform the word into a different thing.
あまり is usually placed before the verb, so in this case you put「あまり」+「泳ぎませんでした」and you get a modified verb "did not swim much".