第二个更准确一些，多来形容学习，是一个程度副词

The second one is correct：我应该多学习中文。 多 is an adjective, means more. Here we use 多 as an adverb before verb 多学习。 “多+verb” indicates a higher frequency or a greater extent on doing something. Hope that helps!😄

The second is right

“我 应该 多 学习 中文。” 这个是对的。 We often use this pattern "多 + Verb" to indicate a greater extent of this action. "多 + verb" is one of the patterns for making suggestions.

the second one. Adv+verb：this adv is used to describe the verb. Eg: 多学习，study more 很喜欢，very love