How many people ordered food in the restaurant? How many people had only a popsicle? 
In restaurant one day we could order Burger, Desert, Salad and Popsicle. People could order anything but only one piece of it, but everyone had to order something. We know that that day they sold 35 Popsicles, 58 Burgers, 16 Salads and 25 Deserts. We know the following information about orders: : PB 21, PS 7, PD 8, BS 13, BD 19, SD 0, PBS 7, PBD 2, PSD 0, BSD 0, PBSD 0 (where PB $n$ means that $n$ guests have ordered AT LEAST a Popsicle and Burger).
1) How many people ordered food that day in the restaurant?
2) How many people had only a popsicle?

Any hint is greatly appreciated. I understand that there was no one who had only soup, since there should be such an order Pn? Or maybe someone could order for other people as well?
And for example when I have PS 7, BS 13, PBS 7 - I know that someone from PS and BS has to be in PBS, but how can I tell whom it was (how many of them from PS and how many from BS?).
EDIT: I apologize, I was translating the text so I tried using appropriate words. The question is not about soup, but about popsicles.
 A: Hint. Apply the  Inclusion-exclusion principle: the number of persons that ordered food that day in the restaurant is given by
$$P+B+S+D-(PB+PS+PD+BS+BD+SD)\\+(PBS+PBD+PSD+BSD)-PBSD$$
where for example $PS$ is the number of persons that had at least Popsicle and Salad which is $7$. 
As regards the number of persons that had only had only a popsicle, consider the formula
$$P−(PB+PS+PD)+(PBS+PBD+PSD)−PBSD.$$
A: 
I know that someone from PS and BS has to be in PBS, but how can I tell whom it was (how many of them from PS and how many from BS?)

You're looking at it backwards. The thing you should ask is: I know that some of the PS are also counted in PBS, but how many of the PS are not in PBS, PBD, or PBSD?

I understand that there was no one who had only soup, since there should be such an order Pn?

My best guess there is that the person who set the question made a mistake. There's no way of knowing how many people ordered soup, but there is a way of calculating how many people only ordered salad. I suspect that the question was rewritten to change S from soup to salad, and that part was overlooked.
