Wordpress Website Speed Issues

My company's wordpress website is performing very poorly on speed tests. I'm looking for someone with experience to be able to correct this for me ASAP. Before you submit a proposal, please check out the site for yourself: raytechinfrared.com. I had it created by a pph user a couple years back and it works great other than the extremely slow loading. I don't want to change any of it if possible, but looking to make it faster and maybe learn what is happening that could be causing this in the future! (Please submit a proposal on a job basis - not per hour - Thank you!)