Am I Going To Lose it All If I Update My Lumia 520?

Am I Going To Lose it All If I Update My Lumia 520? - 1
Added (1). I have nokia lumia 520 and i havent updated it since i bought it. So i want to update it now but what i want to know is

1. If i update my phone to new version will i lose my contacts,apps & text messages?
2.& if i lose it then can you guys tell me how to recover it if from its back up?
3.& how to take backup of contacts? Thank you

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