Couple things...there's tons to learn so ask questions. Pay close attention to the weather and wind speed. If you have a consistent 15mph wind that is ideal, flying the kite like you did in 10-12mph is fine too, you won't be riding in that wind but you can body drag and learn the ins and outs of keeping the kite in the air and relaunching it.
Fronts, storms, etc, anything creating unpredictable wind is always to be wary of, but as a beginner more so. 15mph is a lot more powerful than 10mph. 20mph wind can easily mess you up big time. The force of the wind basically is 4x stronger when the wind doubles. You'll get to the point when you know exactly when you are in 18mph vs 16mph b/c of the amount of more power you have just in that little increase.
I used a strong bag filled with 100lbs of sand when I was launching solo back in the day...That will teach you where to put the bag and how not to hot launch your helper lmfao
Pick that kite up a little too far downwind of your bag setup and that kites gonna put you on your ass if it's blowing. You have no clue how strong a kite can be yet, so be careful.
There's zero reason you should have any problem with attaching your lines. As said, rig up downwind of your kite for the time being so you can see everything going to the kite. No line should be on top of any other line. The outside lines from the bar attach to the outside points of the kite. And the center lines attached to the center bridles of the kite, therefore by design, no line should cross another line. Grab those lines at the bar and place the center lines inside your legs and have the outside lines outside your legs and walk to the kite. Simple.
If your bar is used, check your lines for wear, or have someone look at them. Line wear as a rookie is just something you probably have no clue about yet. Your bridles can wear out too so have someone look at those. Make sure you know what kite size to use as well. There was a time when I was a rookie and I hadn't bought a 9m kite yet. I missed a bunch of strong wind days, but to be honest, I was not ready for those days even after 4 months. I rode my whole windy season without the 9m and skipped those 22-30mph days. I still prefer my 12m right at 22mph. That's my favorite wind and kite size. Make a mistake with your bar inputs boosting a large jump on a 9m in 30mph and it just aint going to end well. At 22mph and a 12m kite I am nicely powered with room for forgiveness, but make no mistake you can ruin your month or year in that wind if you try.
If you want to see how much power 20mph wind is watch some videos of Toby, the mod here. He basically only rides in that wind and rigs a massive kite for airtime. Anytime I see his videos my abs just clench up b/c I know how much power he's riding with.