mmm well...what's causing you a hard time exactly? I don't know your level of Japanese...
If you want to describe something is good in your opinion, a polite example: how about something like: このゲームは Dark Souls 3 を申します、良いゲームですと思います。Kono geemu ha, DarkSouls3 wo moushimasu (polite form of mousu), yoi/ii geemu desu to omoimasu.
(This game (topic), it's called Dark Souls3, I think it's a good game.)
So if someone asked you what you like about it, which words and adjectives would you use? いい、おもしろい、たのしい...
Some important stuff: 良い is read as よい yoi or いい ii meaning 'good', AND THE IMPORTANT THING TO REMEMBER ABOUT THIS I-ADJECTIVE IS THE CONJUGATION: IT'S ALWAYS CONJUGATED BASED ON THE よい (something was good -> よかった. And usually desu follows after that. Politeness is good to keep in mind). :P
:D