Yes, the original data brought into the FamilySearch Family Tree came from various original sources and personal trees. It all came in as submitted by FamilySearch. It does not mean it is incorrect, but you should try to verify record sources as you put your family together. You can merge duplicates and build relationships between individuals to make the tree cohesive. Remember that goal of FamilySearch Family Tree is one single, interconnected, world-wide tree, so many people will be able to work on the same individuals that you work on.
Yes, as you merge duplicates, you must move information from the right-hand side of the screen to 'add' it to the final visible record of that person. All sources automatically are added to the final remaining individual record, but everything else on the right-hand side must be added to the left-hand side in order to show in the final record. Note that as you merge records and add information from the right-hand individual into the left-hand individual, it changes the submitter to your username, so it appears as if you added the information.
Anne thank you for your answer. I did make a really stupid mistake but I've corrected that and my brain. However, I have come across new census records that I know are my family but there seems to be serious transcription errors. The male ancestor surname is spelt wrong or actually truncated but his wife has the correct surname. Shouldn't the transcription be corrected first before merging. I am definitely into One family. Thank you again.