Assuming the soreness is DOMS… You might be closer than you think to getting to that point. If you can, take a listen to
DOMS is unpredictable, but usually “the way out is through.” Some people suffer from DOMS every time, but as far as I can tell that’s pretty uncommon. More typically, the first 2-4 weeks of regular strength training is the worst for DOMS; and yes suffering through DOMS for 2-4 weeks sucks. It’s hard to suffer through for that long and have anything but complete skepticism that DOMS will go away, but for most people it really does!
As I understand it, the keys to breaking past DOMS are 1- consistency and 2- consistency. But it’s important to be consistent about applying those two rules. 
Sticking with 2-3 days per week, getting 1-2 days of rest between each workout, and keeping the weights pretty consistent (even if it seems easy for the routine you’re practicing, I’d still encourage consistent incremental increases over the matter of a couple of weeks vs. immediately adding another 20kgs/45lbs).
For deadlift specifically, you don’t say what exactly is sore or how. For example, if your back is sore: it’s probably not DOMS, and you need to look at your form possibly with a trainer.