Using 'lassen' to let and get things done
The German verb lassen is incredibly versatile. When you pair it with another verb in its infinitive form, it describes either letting something happen or arranging for something to be done. English speakers often trip over this construction because English uses several different verbs for these ideas, such as let, have, get, or make.
Another common mistake is trying to insert the word zu before the second verb. Just like modal verbs, lassen combines directly with the infinitive. You will see this pattern in standalone combinations as well as set phrases like fallen lassen and sich scheiden lassen.
At its core, lassen followed by an infinitive has two main functions. The first is permission, similar to the English let or allow. The second is having things done, which means you arrange for someone else to do a task, similar to the English have or get.
You can also use this construction for things you have done to yourself, like getting a haircut (sich die Haare schneiden lassen) or leaving things as they are (stehen lassen).
German frequently links lassen with specific verbs to express concepts that usually require just one word in English. For instance, fallen lassen literally means to let fall, but we translate it as to drop. Similarly, liegen lassen (to let lie) means to leave something behind or forget it.
This also applies to more mechanical actions, like removing liquid from a container.
Some fixed expressions use lassen alongside a reflexive pronoun (sich). A very common one is sich scheiden lassen, which means to get a divorce. Another useful phrase is sich entgehen lassen, meaning to miss a chance. Notice that the latter takes a dative pronoun, like mir or dir, because the opportunity escapes from you.
When you want to talk about the past using the perfect tense, there is a special rule. Normally, you would use the past participle gelassen. However, when lassen is paired with an infinitive, it drops the ge- prefix and acts like an infinitive itself. This creates a double infinitive at the end of the sentence.
When you want to express letting something happen or arranging for something to be done, pair lassen with the infinitive of your action verb. Never add zu between them. If you are speaking in the perfect tense, remember to use the double infinitive rule and place lassen in its basic form at the very end of the sentence.