Translation:I travel by myself often.
"一人" is pronounced as "ひとり" when saying "alone". Unfortunately, DuoLingo doesn't really make a difference between the on'yomi (Chinese reading) or kun'yomi (Japanese reading) and oftentimes has the kanji said one way in a sentence, but said a different way when you select the kanji by itself. So "hitori" is how you would say "alone". But the kanji "一人" can ALSO be read as "Kazuhito" which is a Japanese masculine given name. But in this sentence, it is read as "hitori". (-:
The で particle, when used in conjunction with numbers and counters, states a certain number used/required for something.So, if you use it with the counter for persons, you can state how many people do a certain activity.
Note also, that it's different to using the particle と as in that would add the number someone does something together with, so the total amount would be higher, then the one specified with と.
I would like someone else to expound on this, but I will say what I think I understand.
たくさん is generally used to say "a lot" or "much" when talking about quantity of something.
あまり seems like a magnifier. Used in the positive it can make there more of something, but used with a negative like あまりにも it takes on a meaning more like hardly. Check out jisho.org for example sentences and definitions.
よく can be used for "often" as in this sentence. Other meanings of this word you'll learn as you encounter them.