Welcome to this optional A2 German revision deck. We'll refresh some of the trickier grammar points to make sure you have a solid foundation before we dive into the B1 material. We'll cover the Perfekt tense, different types of prepositions, modal verbs in the past tense, comparatives and superlatives, and basic subordinate clauses. Let's get started.

Let's start with the Perfekt tense, which is used to talk about the past, especially in spoken German. It's formed with an auxiliary verb, either 'haben' or 'sein', and a past participle. The key is knowing which auxiliary to use. Most verbs use 'haben'. The main exceptions are verbs that show movement from one place to another, like 'gehen' for to go, or 'fliegen' for to fly. Also, verbs that show a change of state, like 'einschlafen' for to fall asleep. These verbs use 'sein'. The verbs 'sein' itself, meaning to be, and 'bleiben', meaning to stay, also use 'sein' as their auxiliary. For everything else, 'haben' is usually the correct choice.