Modal verbs add an attitude to another verb: ability, necessity, permission, wish. There are six: können (can), müssen (must), wollen (want), dürfen (be allowed), sollen (be supposed to), mögen / möchten (like / would like). Two rules cover almost everything: 1. The modal is conjugated in position two, and the MAIN verb goes to the very end as a bare infinitive. Ich muss heute früh aufstehen. 2. In the ich and er/sie/es forms the modal takes NO ending — ich kann, er kann. Not er kannt. Most modals also change their vowel in the singular: können → ich kann, müssen → ich muss, dürfen → ich darf.
In Persian the two verbs stay next to each other — «باید زود بیدار شوم» keeps باید and the main verb close together. German separates them across the whole sentence, and everything else piles up in between. Practise building long middles: Ich muss morgen früh mit dem Bus zur Arbeit FAHREN. Getting comfortable with that gap is what makes you sound German rather than translated.