[Q] Android permissions topic

Hello everyone,

since am new to android os and i recently came from iOS, i do have some questions about how android apps work. first of all i noticed the lack of permissions you can choose to give to spesific apps like iOS allows, when i try to install an app from play store, it just shows me what permissions the app is going to use and thats all, they dont allow me to change that? and my biggest complain is that i downloaded viber from play store before one day, and the app modified my contacts list app adding viber out/free viber calls shortcuts.. for me thats unacceptable, i mean its like installing an app on your pc and not being able to deny the toolbar that comes within it to your browser.. how can i change all that and control the freedom of the apps. btw sorry for my bad english, i hope you ppl can understand me