I would recommend that you do some research about the three companies you mention and then if you are not sure go to the correct Topic e.g. Royal Mail (RMG) 📮 💌 - Share Chat to ask some specific questions. I would also be careful about what you read on these forums especially by people who have bought in to a stock. This is the internet after all - you have no idea who these people are and what their level of competence is.
Learn more about investing through Learn about investing with Freetrade’s guides and by going to some of the sources in The ultimate list of investing books, podcasts and blogs v2 💡.
Oh and @SebReitz’s suggestion to buy a general index ETF is good advice. But first read more about that too - as there is much to be aware of. The links before will also help you understand ETFs. For additional information see for example Passive Investors - ETF Portfolio Discussion.