What are the classic textbooks of functional analysis, real analysis and complex analysis?
Tao Zhexuan's real analysis is very good. Unfortunately, Dangdang and Zhuoyue are out of stock. You can go to Dangdang to see the others. For complex analysis, see complex analysis: visualization method, for functional analysis, functional analysis (2nd edition of the original book)-zhanghua Mathematics Translation Series. You can find these wherever you go. In short, it is better to look at these foreign branches of advanced mathematics. (Personal advice only, don't worship foreign things)