Can anyone tell me whether I will lose all my contacts if I reset my phone?

What kind of phone do you have? What is your default back up method?

Meaningful pictures that were messaged to you, save to your phone (and then back up).

Samsung galaxy 5, and I have most things backed up on my computer, or backed up on google.

Call the maker hotline?
Find a store for your plan, or phone store.
If I have my usual ‘I have no idea’ moments, I call on SIRI and after she says: You again? or Quit it, leave me alone already!
then I’ll ask my Q, and she has found internet articles faster than I could scan for them myself.
It’s only bad in public when she gets snippy. She humiliates me. :)
You might be surprized what someone selling the tech in the big stores can do or know. Brand knowledge is their business. They are pretty savvy also.
I hope it works. Good luck!