Resolved questions
when do you use article "het" and "de"? what is the difference?

It's kinda like the German "die, der, das" particles, except in Dutch we only have "de" and "het". Unfortunately there is no way to know which one to use, you have to learn all of them by heart. Of course there are a few shortcuts. One is that you always have to use "het" when the word is used in its 'small' form. Ex:
Het huis (the house) --> het huisje (the little house)
De man (the man) --> het mannetje (the little man)
De school (the school) --> het schooltje (the little school)