Does this sentence sound ok in English?
The political decisions will be reflected on stock prices in a short period of time.
If it doesn't, what verb or structure should I use?
The sentence is mostly fine BTW except for the use of on instead of in.
The political decisions will be reflected in stock prices in a short period of time.
The sentence structure depends on your audience. Please state your concern with the sentence structure so the community can be of further help.