Does anyone actually say 'bed sheets'? I don't think I've ever heard that...
The Esperanto verb kuŝi is equivalent to the English verb "to lie", as in "to recline in a horizontal position". This is not to be confused with the English verb "to lay", which refers to the transitive action of putting something down (e.g. "He lays his phone down on the counter")
Note also that, to add to the confusion, the English verb "to lie" conjugated into past tense, is "lay" (E.g. "Yesterday, he lay in bed sick").
A few example sentences of the correct usage of the verbs in English:
→ "As soon as I get home, I am laying my phone on my table to charge and I am lying down to take a nap."
→ "My cat didn't want to be held, so I laid her on the floor."
→ "Last night I lay awake for a long time."
I hope this helps!
The first one sounds weird; native speakers would actually say, "As soon as I get home, I lay my phone on my table to charge and I lie down to take a nap."
When asked, "What are you doing?" would be when one might reply with "I am lying down to take a nap."
Perhaps I didn't word it in the best way (I am a native English-speaker :)), I meant it in the sense of "As soon as... I will lay my phone" or "I am going to lay my phone..." Sorry for the confusion! Perhaps the way I worded it is more midwestern-American... I'm not sure