Help! First call from Tenant with an issue

[Jay Patel]

Hey BP,

I purchased my first SFR back in March and got it rented out on April 1st. The tenants have been quiet so far but today they texted with their first issue:

Water is slow to go down the shower. When the toilet is flushed while showering, the water level in the toilet rises high (close to over topping). The toilet bubbles when the bathroom sink is in use. They said they tried drainol on in the shower but its still the same. 

What do I do? I am not really handy by nature. 

Thanks!