Knitting Pattern: Recalculate One Size Smaller

Hello dear users and authors 
First of all: great forum! 
Now to my question: 
I downloaded a knitting pattern here for a children’s jacket. Today I measured my grandson and realized that 98/104 is too big. One size smaller would be more than enough. 
How can I recalculate the pattern? Especially the increases? 
It’s this pattern: 
https://www.crazypatterns.net/de/zip/open/59474/0/cf0f02a2a83829853ef9e89f1e753cfdccecfacfdda578951466fc4ef0cd8d64/strickanleitung-kinderjacke-martha-matthis-in-den-groessen-98-bis-128-0.pdf

I would appreciate any help. 
Best regards, 
Tanja 

Dear Tanja,
I would recommend that you contact the author of this pattern using the contact button. You’ll usually receive a quick and professional response.
Best regards
Petra

Hi Petra,
thanks for your reply.
I’ve written to the author. 😊
Best regards, Tanja