Using research paper as guidance vs research plagiarism?
There's nothing wrong with replicating a paper as long as you cite and credit it. If you pass it off as your original contribution, that's never okay, but science works by advancing on previous work and it's not expected for any work to be completely novel from top to bottom (nor is it desirable).
If all you do is make some minor improvements on something already published, though, that may not be research per se, even if it is still a good exercise for a beginner. Whether that's sufficient for some competition you might submit to is up to the standards of that competition. As long as you are up front about what you have borrowed and where you've borrowed it from, you are in the clear ethically, but it's possible your project won't be judged as highly - it all depends on what those criteria are.
When you make improvements and advancements, it's also important to be honest and thoughtful about where those ideas came from, too. They can still be your contributions, but if you got the motivation from some other source then you need to cite the source. It's good to keep some documentation of the things you've read because it can become difficult to remember where exactly you got an idea from and you may even inadvertently fool yourself into believing you came up with something that you actually read days or weeks ago.
Also, be wary when actually writing up a paper that it isn't enough to make something &quot;your own words&quot; just by restructuring sentences and replacing words with a thesaurus. Your &quot;own words&quot; should come from your own head, without making close reference to another document except to refer to where specifically your ideas and knowledge are coming from.