My step-father and I have a long-standing joke in which I will tell him "don't drop the soap" (because he's in prison). I'm writing him a letter and I want to say this in German. I have two German textbooks, but they aren't very helpful in this case. I looked up what "to drop" is in German and I found that fallen lassen means what I want, but I don't know if I'm using it right. I wrote "Fall (du) nicht die Seife gelassen." Google translate and other websites keep giving me different results, so I have no idea which is correct.
I'm assuming, you're having for example a phone call with your step-father at the end of which you might say: "Bye! And, oh, don't drop the soap!" In this case in my opinion the correct version would be:
Lass nicht die Seife fallen!
As you can see in the comments, there are a lot of ways to add or remove shades of meaning by changing the word order (emphasis) or adding flavouring particles. If you substantiate the particular context, you might get an answer even more precise. Otherwise this should do!