Economy is crucial for our life, so each country has its own standard for importing and exporting products, it is different from one country to another.
... This sentence is poorly organized. You need to rephrase this.
Bringing products from outside has greatcan greatly affect on the markets and on the home grown products, this has a negative and postive affects, on one hand , domestic vegetables and fruits in some countries cant supply the great number of people ,so those goverments should put a good system for importing fruits and vegetables from outside, surely this can have an influence on the prize of vegetables and fruits on the markets,and also on the homegrown products .
.... this sentence is too very long. It runs to almost three lines. Avoid such lengthy sentences because you tend to get carried away at the end. Also, the reader has to memorize so many details to keep a track of what you say. The reader does not like it for sure, and your aim should be to please the reader :D