My wash basin and shower are situated next to each other. When the water
Drains from the wash basin it gurgles in the shower drain pipe and the wash basin pipe. Ive checked for blockages and used washing soda in the pipes.
It still gurgles.

Welcome to The Plumbing Page at AMHD.com.
The sound you hear is being pulled through the trap as it attempts to vent.
You have a blocked lavatory roof vent. Snake from the roof, put out enough snake to reach to base and 15 feet more. Good luck, Tom