How do I know which tense to use?

In German we have 6 tenses:1 for the present tense, 3 for the past tense and two describe something in the future. We call them Praesens, Perfekt, Praeteritum, Plusquamperfekt , Futur 1 and Futur 2. The first one is the present tense and the last two describe the future. The last two are easy to understand because you have them in english too. Say for example you want to ask your parents whether you can visit your friend tomorrow evening but they dont want you to go until you do your homework. To say that you will visit your friend is the simple future tense which is Futur 1 (Ich werde meinen Freund besuchen). To put your parents at ease you want to tell them that you will have done your homework before your meet your friends (Ich werde meine Hausaufgaben gemacht haben). Very similar to english you say "Ich werde gemacht haben" which is "I will have done" for Futur 2. The more challenging part is choosing the past tense. But as a rule, when you are speaking to someone i.e. in everyday language you will typically use Perfekt. Take the example with your homework again. If tomorrow comes and you want to tell your parents you have done/you did your homework , you would say: "Ich habe meine Hausaufgaben gemacht". We can talk about you create this in a bit. Praeteritum is the second of the three past tenses but this is more commonly used in written word , for instance if you read a German "Maerchen" or fairytale. The Plusquamperfekt (the third of the past tenses) is also a tense you will use in english and works in the same way as Futur 2. This is something you had done or as you would say in German "hatte gemacht". So if in two days time, your parents ask you why you went to meet your friends without having done your homework you say "ich hatte meine Hausaufgaben gemacht". Pay attention to where in the sentence you put the two verbs. Notice again the "gemacht". I recommend learning how to form the Perfekt first because 1)that is the most commonly used past tense and 2)knowing how to form it will make it easy to form the Plusquamperfekt and the Futur 2.