Help in Reverse a string you entered using MicroASM software

[kamaoako]

heres the code i wrote its not working yet need a little help only know a few assembly commands so not really good with it yet.

.data
msg1 db 'Enter a word (max 20 characters): $'
msg2 db 13,10m, 'The Reverse: $'
str db 22 dup(0)
buffer db 22,23 dup(0)
.code
.startup

xor ax,ax
xor bx,bx

lea dx,msg1 ;display msg1
mov ah,9
int 21h

mov ah,0ah
lea dx,buffer
int 21h

lea di,buffer+1
lea al,[di]

mov bx[al]  ;heres the part where im stuck at.

lea dx,msg2
mov ah,9
int 21h

display:
mov dl,str[bx]
mov ah,2
int 21h
dec bx
loop display

mov ah,4ch
int 21h

end

i'm a slow learner so bear with me if i cant right away understand what you might be telling me.

any help or tips or opinions will really matter.

thanks