2000 Ford Focus AC bad smell and not working

I was driving around yesterday and thought I smelled something burning. I checked my gauges, all normal. Couldn’t tell if it was from the ac or something outside. Shortly after the ac went from blowing kind of cool air to warmer air. I already thought it needed a charging. So I bought the 134 can of freon with oil and sealant and put it in. This afternoon it was working great, until I was almost home. I smelled that burning smell and car went from nice cold air to warm air again. I do not know what is causing this. Any ideas?

You could have a compressor locking up and dying. You need to have a mechanic look at it. Pressures need to read, the belt needs to be inspected, and the system checked for leaks.