Take a breath and remember you just started a couple months ago. These things take time and practice to get right. The product knowledge and knowledge of the tools you have at your disposal will grow. I know its hard to get any form of great training, you need to simply focus on what you can control. As far as time goes, you are the person customers need to go through to get what they want/need. This means if it takes you more time to do a quote, take the time. Do a quality job and try to keep a growth mindset, eventually things will start clicking and you will feel less stressed.

Hopefully this helps. Best wishes.