Given that we're talking about dinosaurs, we can't really know these things, but I can make educated guesses, based on what I know about large reptiles.
1) How long it take to swallow the guy.
The dinosaur is in a hurry, so probably about 3 to 5 minutes.
2) how long till it starts digesting him?
Digestion will begin as soon as eating does. Saliva in the mouth begins the digestive process. Once some food hits the stomach, the stomach acids are released immediately.
3) How long it take to digest the guy ?
2 to 4 days.
4) will it be able to digest his T shirt and white shorts and underwear.
No. The stomach acids will damage and fade them, but not completely digest them.
5) given it looks like he is packing a large amount in his shorts ,jow long would it take to digest it, will the Dino like digesting it.
Because there are no bones and no muscle in the area, it will be digested quickly - probably within a few hours. The dinosaur won't know what is being digested in his stomach, but he will certainly like the feeling of fullness after a good meal.
6) What if anything will be left once digestion is complete ?
The clothing, hair, an d possibly large thick bones, such as in the skull.
7) Waht would be in it`s dung?
The damaged clothing, some hair, and pieces of bone. Nothing else would be identifiable.