Calls are dropped in sleep focus

In any focus calls (other than those you have set the focus to accept) should go to voicemail, they shouldn’t be dropped. But if the caller disconnects before the voicemail answers it may appear that they were dropped. The way to check is to open the Phone app and look at Recents. A call that was dropped will not appear in Recents, but one that went to voicemail will be listed.

Hello VIK_777,

Can you provide us with more details about the calls dropping? Are they going straight to voicemail? Are you answering them before they drop? This information will help us get a better understanding of what you mean.

This section of the iPhone User Guide has additional information about customizing Focus settings: Set up a Focus on iPhone - Apple Support

We look forward to hearing back from you. Take care.

What do you mean by "dropped"? If you're on a call, what focus mode you have set should not make any difference.

The defaults for sleep mode are to send all calls to voicemail unless you've specified otherwise.