And here are the -n verbs. These verbs are ones that you absolutely must memorize. There are highly irregular, but they are also some of the most basic building blocks in German grammar. Haben and sein are used in the perfect tenses and werden is used in the future and passive tenses. There are various different ways to categorize verbs, but one of the more important ones is whether a verb is weak or strong.
Strong verbs have a mind of their own, bucking the rules.
They follow their own set of rules, if they follow any rule at all. Luckily a good portion of verbs are weak verbs. The few that buck the system must be memorized to a certain extent. Be on the lookout for these unruly verbs and try to practice them. It will make your life much easier.