Learn Dutch: Wij zijn blij met het resultaat. - We are happy with the result.

In Dutch, being happy or glad about a specific thing uses the fixed combination blij met. English happens to also use "happy with" for results, but you should always memorize blij met as a set phrase because prepositions often change between languages.

Could I use gelukkig instead of blij in this sentence?

It is much more natural to use blij here. Blij means you are glad or pleased about a specific thing or situation, like a good result. Gelukkig is usually for a deeper, long-term state of happiness, or it can mean "lucky."

Why is the article het used before resultaat?

Resultaat is a neuter noun, so it takes het instead of de. As a helpful trick, most Dutch words ending in -aat (like het apparaat or het klimaat) are het words.

Is it okay to say we instead of wij in this sentence?

Yes, absolutely! Wij puts a little more emphasis on the group being happy (as opposed to someone else). If you just want to state the fact without extra emphasis, you can use the unstressed version: We zijn blij met het resultaat.