The enterprise game is about building corporations, increasing their value and expanding by both the buildup of new corporations and by purchasing ones both from enterprises and from countries.
Countries can prevent it but will be wrong to do so as they earn a lot of money from enterprise owned corporations.
You should make sure you produce products that are in short supply, (many are), upgrade them and make sure they increase in value.
then, the chance they take them over is smaller because of the high price, and if someone buys them, you receive a large amount of money.
Corporations cannot be purchased in the first 48 months which gives them some time to increase their market value.
This is a very recent extension of the period which I forgot to mention n the game update news.
I will add it now.