how to solve red alarm on my Apple Watch series 3

Hi Timmmaa,

Welcome to the Appl Community.

If the "Related Article" above your question hasn't helped,

then I guess it is not the red exclamation mark in a circle that you are seeing on your watch.

Perhaps it is the "red battery is low" symbol ... like a lightning bolt ?

Status icons and symbols on Apple Watch – Apple Support

or

Discussion thread about restarting due to red showing on Watch:

Apple Watch series 3 - Apple Community

Ej=lse:

There is an "Apple Watch User Guide" available online :

(Choose the Operating System of your Watch at the top. 

You can click on "Table of Contents" to see what's available)

Apple Watch User Guide – Apple Support

or

To view the user guide from the Apple Watch app

Open the Apple Watch app on your iPhone.

Tap Discover at the bottom-right, then tap User Guide.

For Support from Apple, if needed:

Apple Watch Support online:

(There is a "Get Support" link at the bottom of their webpage:)

Apple Watch - Official Apple Support

Hope something here is of help, in some small way :)