A category theory diagram (Need Help)

Question

I am a beginner in latex. Please help me draw this category theory diagram via latex. I have tried this code, but working:

\begin{tikzcd}
A \arrow[dd, bend right, shift right=2] \arrow[rrr, bend left, shift left] &  &  & B \arrow[lll, bend left, shift left] \arrow[dd, bend left, shift left=2] & \colon  & P \\
                                                                           &  &  &                                                                          &         &   \\
C \arrow[uu, bend right, shift right=2]                                    &  &  & D \arrow[uu, bend left] \arrow[lll]                                      & \colon  & Q
\end{tikzcd}

Answer 1

Something like this seems to do what you want:

\documentclass{article}
\usepackage{tikz-cd}
\begin{document}
\begin{tikzcd}[column sep=4em,row sep=4em,/tikz/column 2/.style={column sep=2em}]
A \arrow[r,bend left,"h"]
\arrow[d,bend right,swap,"f"]
    & C \arrow[l,bend left,"k"] \arrow[d,bend right,swap,"s"] &  : P\\
B \arrow[u,bend right,swap,"g"] & D \arrow[l]\arrow[u,bend right,swap,"t"] & : Q
\end{tikzcd}
\end{document}