It's been slightly over a month since the status changed to "Reviews completed." It can take several weeks for the editor to take a decision on your manuscript. This can happen if there are a lot of manuscript queued up before yours. Your manuscript is waiting for it's turn for the editor to take a look at it and arrive at a decision based on the reviews. Don't worry, this is just standard procedure. It does not indicate either a rejection or an acceptance. You will have to wait for the decision letter to know the fate of your paper. However, the fact that the editor has replied to your email is a sign that the journal is actively processing your paper. Keep your fingers crossed! All the best!