1. Learning at least one foreign language is necessary for us.

→ S + be + necessary for + O

2. You should not take these painkillers very often.

→ S + should (not) + V_inf

3. I don't feel like going out tonight.

→ S + do/does + not + feel + V_ing 

4. Do you mind if I ask you my question?

→ Do you mind if I + V_inf?

1. Learning at least one foreign language is necessary for us.

- It is necessary for sb to do sth: nó cần thiết cho ai đó làm gì..

= Ving (danh động từ) + tobe + adj + (for sb)

2. You should not take these painillers very often.

- Should not do sth: không nên làm gì..

3. I don't feel like going out tonight. Do you mind if I ask you my question?

- Not want to do sth = Not feel like doing sth: không muốn/cảm thấy không thích làm gì..

- Do you mind if + S + V(s,es) ?: Bạn có phiền không nếu ai đó làm gì..?