Concurrent workers independently published part of my results. How to convince the referees that I got the results independently? In my primary research project (not coauthoring with advisor), I got two results, say result A and result B, back in 2020. I wanted to submit it in 2020, but my advisor says that I need a further result, say result C, to be considered for a top journal.
I agreed with him as I find the (hypothetical) result C way more exciting. Now I am half-way through getting result C.
A competing group tried to get result A (with mistakes) and submitted a paper in 2020. The referee rejected their paper because they made a fatal mistake. They corrected the mistake and submitted the corrected version of result A again. They got their paper accepted at a top journal in March 2021.
I don't know how to speak with my advisor about this without offending him. My advisor says it is a good thing as it proves that I was at the right direction and a super active subfield. I think he is just trying to sooth me by saying nice words.
Now I am submitting the results A and B by myself. I do have timestamps on public cloud services to prove that I did get the correct version of result A before them. However, the timestamp is just on a poorly written draft rather than a fully written paper, because my advisor asked me to work on C.
It is my first time dealing with this issue. Shall I also submit the timestamps to prove that I had the result A?
I am thinking about putting result A into appendix and emphasizing result B in my paper. Am I correct? Is it best to submit the paper to the same journal?
I will cite their paper of course. I want to say that I am a concurrent worker work in parallel. I am afraid that the everyone think I am the follower, who falsely and unethically present myself as a concurrent worker.
What shall I say to make clear in my paper what happened?

PS:
I was not worrying before March because I thought:

The competing group made mistakes so they are not competent competitors

Result A alone is not enough for top publications. Their paper still contains some technical mistakes and exaggerated claims.


However, facts proved that I underestimated the competing group. The hard lesson learnt.
The field is applied statistics. This is a primarily theoretical work that studies the properties of two widely-adopted statistical methods.
Related: Pre-print service like arXiv but with private option, so I can correct my mistakes without publicly advertising my mistakes?
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.