Scales to Play Over C#m11
Every chord is a subset of several scales: any scale that contains all of a chord's tones fits over it. Pick a chord to see the matching scales from its own root, the major keys the chord belongs to, and full fretboard diagrams for every scale on guitar.
A C#m11 chord contains the notes C# – D# – E – F# – G# – B. Any scale that includes every one of those 6 tones fits over it — from the root C#, that means C# Natural Minor, C# Dorian and C# Dorian Bebop. Start with the first scale listed: it is the most common choice, and the others color the same chord tones differently.
C#m11 is also diatonic to 2 major keys: B major (relative minor G#m), E major (relative minor C#m). In a song from one of those keys you can also solo with the key's own major scale or its relative minor pentatonic across the whole progression, not just this chord.