I'm doing a practice paper for a past mathematical modelling exam. I've attached the problem

What I'm having trouble with is simplifying the equations and variables into a differential equation that is solvable with Euler's Method.

What I have currently is the sqrt(h1-h2) in the equation which leads to an imaginary number so I don't think I have done it correctly. ( As h1<h2..I think the diagram is also misleading)

If someone could help me out with getting the right equation I should(hopefully) be able to do the next part.

The second question doesnt need to be attached, it is:

Use Euler's method to make a single step to predict the levels in both tanks after 5 seconds.

Thanks