simnoyofqgttj pqdtfqrtrqpzt fobuuopszrziy uzaqufshdziqo ttzrkfshyrqof ztqztdhsppodt ugrgugpqnuyyh qudqypzdtkmto xqzzteguyddzs tugqdqiphlbqu losubyqzdzlsq pytukiojbprqk gzdytqygthjzp

I found his Key but I don't know how to proceed:

a b c d e f g h i j k l m n o p q r s t u v w x y z

S N V F R G H J O K L A Z M P Q W T D Y I B E C U X


I noticed also all letter clumps have 13 letters.

I think there's a letter missing at the end because the message reads:

listen to me kid you need to turn back now and leave town do not trust the treacherous sadiq or you will find yourself floating down a river face down with a knife in your back when you are no longer useful to hi

And you can unravel it by:

1. Arrange the 13-letter blocks into a 13 x 13 grid, one above the other:

  a   u   n   b   i   t   i   d   p   f   r   r   h
o   p   s   r   d   p   e   r   e   p   o   m   r
d   i   v   y   y   i   o   a   m   e   m   u   t
y   m   l   p   y   d   a   g   s   m   u   p   i
r   r   m   e   j   d   a   g   t   e   p   i   d
m   r   p   m   r   s   g   a   o   o   i   s   r
y   f   e   f   y   f   o   p   b   y   t   t   g
p   y   s   p   t   o   m   s   r   j   n   r   i
z   p   m   m   r   w   f   y   t   s   s   m   a
r   y   f   p   s   p   u   o   g   l   v   p   y
l   i   a   y   v   t   p   m   s   m   l   a   p
o   t   r   y   j   u   i   h   v   o   e   p   j
f   m   s   t   r   p   t   f   r   g   j   m   o

2. Use the key to replace all the letters in the grid (note: take the letter from the grid and look up the capital letter from the key and replace it with the corresponding lower-case letter)
  l   y   b   v   u   r   u   s   o   d   e   e   g
i   o   a   e   s   o   w   e   w   o   i   n   e
s   u   c   t   t   u   i   l   n   w   n   y   r
t   n   k   o   t   s   l   f   a   n   y   o   u
e   e   n   w   h   s   l   f   r   w   o   u   s
n   e   o   n   e   a   f   l   i   i   u   a   e
t   d   w   d   t   d   i   o   v   t   r   r   f
o   t   a   o   r   i   n   a   e   h   b   e   u
m   o   n   n   e   q   d   t   r   a   a   n   l
e   t   d   o   a   o   y   i   f   k   c   o   t
k   u   l   t   c   r   o   n   a   n   k   l   o
i   r   e   t   h   y   u   g   c   i   w   o   h
d   n   a   r   e   o   r   d   e   f   h   n   i