Did you come across structures like "in terms of"?
What does it exactly mean, and how do we use this structure?

It's mainly used for asking or giving information about how one thing corresponds to or relates with another.「でいうと」の文法を使います。

We find this grammar used in business context. E.g. 
In terms of price, this model is better, because for the same price, we have 20% more battery life.このモデルは同じ価格でバッテリーの使用可能時間が20%多くなるので、より良いです。

In terms of difficulty, the last exam was easier than I thought.
難しさでいうと、最後の試験は思ったより簡単でした。

But of course, we also use it in casual conversations.
For example, in terms of weather, I prefer spring much more.
天気でいうと、春がずっと好きです。

In terms of learning a language, what do you think?
Well, in this sentence, it might be better to use に関して。
言語を学ぶことに関して、どう思いますか。