See https://help.researchgate.net/hc/en-us/articles/14293099743121-How-to-make-content-private-or-remove-it for instructions. However, when you delete the page for a paper, "Reads", possible citations etc. will get lost. A better solution is to merge the two pages. See the section "Why are there duplicate research items on my profile?" in the help page https://help.researchgate.net/hc/en-us/articles/14293081125777-Reviewing-editing-and-featuring-your-research to get instructions how to merge two entries.