What is maggiorana and how can I use it

Marjoram is botanically an oregano subspecies, but it does taste entirely different (a situation very common in herbs, think spearmint and peppermint). The description "smells almost like tea and is almost tasteless" indicates that you got mass-produced stuff where the good aromas have long left the dried plant matter. Fresh marjoram is a rather mild herb, but it still has a distinct aroma, and not a generally "grassy" one.

The aroma of majoran isn't very intrusive, so it can easily be combined with many flavors. It is very often used with potato dishes of any kind, but a big herb producer recommends it for practically everything:

Potato soup and salad, potato dumplings and fried potatoes, meat and sausage salad, all salty cheese dishes, meat loaf, chicken fillings, and especially to homemade lard, duck and goose, rabbit and pork fat. Marjoram is good also for dark mushrooms, cucumbers, all bean dishes and feed legumes, stuffed tomatoes and tomato soup, carrots, peas, sour cream sauce, herb mayonnaise and herb cheese, all heart, liver, kidney, lung dishes, tripe, fish soups and fish stews, fish baked in fat, pie fillings, soups and wild game stew.

It would have been perfect if you had the fresh stuff, but even the dried herb is better than nothing. Just add it to some dish (you can use big amounts, because it is already weak) and decide if you like it.