You can find free sonnerie telephone for your Android phone on specialized websites, ringtone apps, or even by searching online. Make sure you choose reliable sources.
No, customizing ringtones generally does not affect the performance of your Android phone. Ringtones are lightweight audio files that should not have any significant impact.
Yes, you can assign different ringtones to each contact in your phonebook. This will allow you to know who is calling you just by hearing the ringtone.