how do you set up an approval step between a form submission and the actual action?

we have a purchase request form that employees fill out. right now the form just dumps into a spreadsheet and someone emails the manager to approve or deny. the manager replies to the email, then someone else manually does the next step (creates the PO, notifies procurement, etc) its slow and stuff falls through the cracks constantly. last month we had 3 requests just sitting in someones inbox for 2 weeks because the manager was on PTO and nobody followed up what i want is something like: employee submits form > manager gets a notification and approves/denies > if approved the workflow automatically does the next steps is this possible here without writing a bunch of code? we tried doing this in zapier before and it got really messy with all the conditional branches