"nie to widzę" = it is not this what I see. "Nie widzę tego" is the right form :)
Well, you can't omit it in English, unless you go with less formal "thanks". And in Polish... it just seems obvious that it's 'you', unless specified otherwise (Dziękujemy im = We are thanking them, for example).
"dziękuję" is the 1st person singular form, "dziękujemy" is 1st person plural.
So you usually say "dziękuję" because that's literally "I thank", but sometimes you say "dziękujemy" (we thank) because you're saying it not only on your behalf. For example if I am with my girlfriend in a restaurant and the waiter brings our food, it's natural to say "dziękujemy" because we both thank him for bringing the food - even if only one of us says it out loud.
Here, the person saying that probably speaks on behalf of their whole company, or something like that.