in the sentence Ich fing an Deutsch zu lernen, there are 2 verbs. The main verb is anfangen, which is in the 2nd position

Your example sentence actually has two parts. The first is a normal clause, with no object. The second is an infinite clause. In an infinite clause, the verb always goes at the end. The objects and any other modifiers come before. Examples: "Ich fange an, Deutsch zu lernen." "Er hat versucht, mir die Tasche zu klauen." Infinite clauses that consist of more than just "zu + verb" should be separated with a comma. This will make it clear which words belong to the infinite clause, and which to the preceding part of the sentence.