What do you think of this restaurant stock (PTLO)? case study in company valuation

Portillos (PTLO) is well known in Chicago area. They had their IPO late last year, it peaked at $54 and is now at $23. They are always busy and they are expanding. As a beginner investor, I'm interested. I feel this is a good case study for someone who is more well versed in valuing companies to give me their 2 cents. Like, what do you look for, and is it currently fair valued?

Thanks