Concurrent workers independently published part of my results. How to convince the referees that I got the results independently?
You've been scooped, I'd say it's common. You could write: Further to publication of our preliminary results [1], X et al. showed ... Or: In parallel with this work, X et al. showed ... (You could cite your technical report elsewhere in the latter instance.) You can then explain how your work improves on theirs, especially as your results are way more exciting.
Your approach to result A may be different to X et al., which may allow you to present the result in the main body. Also, your result A may be slightly different to their result A (i.e., you may have slightly different results). Speak to your advisor about how to approach this.