你最好看一下医生 You'd better see a doctor. 看医生【see a doctor】
不要独自在河中游泳 Don't go swimming in the river alone. 独自【alone】
我可以结账了吗? May I pay the bill ? 结账,买单【pay bill】
没关系 【Never mind.】【It's OK.】 【No problem~】
那个穿红色衣服的女孩是谁? Who is the girl in red clothes ?
You had better go and see a doctor.
注
had better +动词原形