Degus can be hard to bond with. I've had 2 of my degus for 6 months now and they still don't trust me as much as I hoped they would by now. Part of the reason is because they were in the pet shop until they were 4 months old and probably never handled while they were there. The other part of the reason is that they just aren't ready to trust yet
I've read degus like being pet/scratched before also and none of my degus (even the ones I hand raised since they were born) will let me pet them. They will run and hop in my hand and let me play with them for hours but they don't like to be pet. I think it is odd if you get a degu that will sit still and let you pet it instead of running around and playing, especially before you've had them for a year or two.
As for biting, all of my degus bite a little. Degus love to chew and they will try to chew anything, even your fingers. They will probably just nibble lightly on your finger just to try it. Most likely if they're doing this they wont draw blood. the important thing to remember is if they start to nibble lightly don't panic and pull your hand away or it might scare them and your bonding will take even longer.
I wouldn't worry too much about your degu not trusting you yet. I'd say give it a few weeks, maybe even a few months. Gradually is the way to take it
If you rush to get your degus to trust you (by constantly picking them up and such) it'll take even longer for them to trust you. It's easiest to sit with your hand in their cage, without moving it even if they nibble, for a little bit to let them get used to you. If they get on your hand while you're doing this don't pick them up just let them explore. Sitting still will help them not to feel intimidated and they'll get used to you easier if they know that they can go about they're normal day with you around
If you can sit there for and hour or two, go for it! The best way to gain your degus trust it to let them come to you. Also as Sasami said, treats help a lot too
As for Myandi taking her treat and running that is normal
Most degus like to eat their treats in private, sometimes even away from other degus. I think that Paprika just needs a little bit of time to get used to her surroundings, she is probably just nervous in the new environment
Also degus don't like to be touched while they're eating, especially when it's a treat because they think you'll take it.
After your degus get used to their surroundings and to you they will race each other to see you also, it just takes time
Degus are great pets after you bond with them
It's the bonding process that takes the longest, but after that they will be very loving to you. Even if they don't let you pet them after you've bonded, they'll show you in their own way that they love you