Hi, what product line are you using and where are you training. Your educator should be able to keep an eye on you and help during class time. Don't be afraid to call her over and ask lots of questions and let her stand and watch you until you are improving.
Blending tips is a skill, and is a difficult one to master...but once you do you'll never lose it.
The best type of tips to use have a micro well, but if you are using full well tips you can cut out part of the well to make them micro. I tended to pre blend tips in that I would file the surface of the tip slightly before applying it. Once applied cut to the right length and thin down the tip from the free edge towards where it meets the nail. Don't go straight to the blend line! Once you have thinned the tip out blending the line will be easier. Always be aware what part of your file is connecting with the tip to ensure you are never filing the natural nail. Long smooth strokes with the file are better than short fast ones as you can cause a friction burn on your poor clients nail bed! Long slow strokes should also ensure you don't overdo it and blend the tip right off!
Another reason they could be snapping off could be it wasn't properly attached, in that there could be air bubbles underneath. Ensure all parts of the well are firmly adhered to the nail before lifting your file.
Regarding your liquid and powder mix ratio, without knowing what product you are using that is a tad tricky.
The system I used was 1 1/2 parts liquid to 1 part powder. To get this right I would dip my brush in my monomer liquid and then in the polymer and once I lifted my brush out with a bead on it I would watch the powder absorbing the liquid counting out 3 seconds. If all the powder was absorbed before 3 seconds then the bead would be too wet so I could dip back into the polymer to get it right. If there was still powder on my bead then it would be too dry and if applied, it will set too quickly and fight back when you try to press it into place! There is nothing you can do with a dry bead but ditch it and try again.
This will be why it is setting in your brush too!
With the correct mix ratio a bead when you place it on the nail will come cleanly off your brush. Then leave it for a second to settle before you start to press and smooth it across the nail. Once finished pressing it out wipe your brush to ensure there is no product on it beforea ou put it back into your monomer to get the next bead.
Stop stressing, these are the 2 main things that frustrated us all when we started out. Take your time, talk to your trainer and it will all eventually fall into place.