Tmux commands doesn't work

You have changed the default escape-sequence in your configuration: from Ctrl-B (tmux default) to Ctrl-A (just like the similar terminal multiplexer screen).

The relevant configuration lines are in the third paragraph:

# unbind default prefix and set it to Ctrl+a
unbind C-b
set -g prefix C-a
bind C-a send-prefix

If you want to use tmux default one just comment out (with a leading #) or remove the lines above in your tmux.conf.