Adjectives can be compared as in 'good, better, best' or 'nice, nicer, the nicest'. Though not all of them. As you may remember, the adjectives of the third declension cannot be compared nor made into adverbs or pronominal adjectives.

Comparative degree

You can make an adjective into the comparative degree by adding a suffix -esn and an ending -is (masculine) or -ė (feminine). For example: geras (good) becomes geresnis; gera (good) becomes geresnė; blogas (bad) becomes blogesnis; bloga (bad) becomes blogesnė.

The new word as if becomes an adjective of the first declension, because it is being declined using the first declension of adjectives with the endings -is and -ė. You may take a look at the first declension of adjectives again.

Jonas geresnis už Petrą. Jonas is better than Petras.
Ji blogesnė nei aš. She is worse than I.
Gyvenu geresniame name negu tavo. I live in a better house than yours.
Gyveni blogesniame name negu mano. You live in a worse house than me.

You can see from the gray sentences that the little comparing words are už, nei and negu which all mean 'than'.

Superlative

An adjective is made into a superlative by adding a -iaus suffix and an ending -ias (masculine) or -ia (feminine). They will be declined by the first declension too, but with a different ending (-ias and -ia). Examples: geras (good) becomes geriausias; gera - geriausia; blogas (bad) - blogiausias; bloga - blogiausia; mažas (small) - mažiausias; etc.

Jis - mažiausias nykštukas pasaulyje. He is the smallest dwarf in the world.

All this is not the hardest thing on earth, but you need to do lots of revising. Why not recall the declensions of adjectives again? If not, you may finally see what's the pronominal adjective or the neuter gender.