SQL server optimization

We have installed sql server 2019 on windows server 2019 on a Hyper V VM. We have assigned 6 cores and 48GB of ram. The problem is that our applications using SQL are extremely slow. We have noticed that SQL service on SQL server never goes more than 280mb... Although we have setup the properties to allow unlimited. We need someone with good knowledge to SQL to fix us this problem.
We will provide remote connection on Vm