So hi there … i want to develop some stuff … games, apps something like that and know my qestion is because when i use graphics, images and so on where i found on the net … for example icons from flaticons.com so many stuff there is described by that “CC BY 3.0. It’s necessary to credit the author” and there even a description here : but so i´m not the best in englisch cause i´m from germany but so my main questions are … can i use this stuff even for commercial usage in form of an app or an game which contains stuff like that ? So when i have to show the licensed from that stuff … do i HAVE TO do it directly in my games/apps or can i even just put an link below a header which says “license evidence” and the link brings you to an link of my website where it opens an pdf where is described for all my apps and all my games what is used and under which license. So it would be awesome if that is allowed cause it would be much lower work for me to do everything in one pdf file as do it seperately in every app or game …cause i have to change my files every time … with one single pdf i can make a list where under each gamename/appname i can write the license.
WOULD BE NICE if anyone can help me with this questions !
AND WOULD BE nicer if i can do so 
So there some more questions :
In generally when i buy something like icons or models … i don´t have to describe from where they are or under which license they are i think cause i bought them … am i right ?
When i use icons from flaticons which are unter these conditions : “CC BY 3.0. It’s necessary to credit the author” as described in the url i´m allowed to use these material for personal and even for commercial usage am i right ? So there is this “It’s necessary to credit the author” means this i´ve to mention it … or means it i have to donate to him ? I want to use free stuff for my projects just until i can afford to buy great stuff.
So my last question is … how is it generally … how should i behave to do it right ?
I don´t want to learn moddeling, texturing and all that stuff … i want to focus most on building and programming good games !
Hope someone can solve my problems 
!