Ich verwende PHP Version 7, soll ich auf 7.2 updaten?

Unfortunately I can not find a satisfactory solution for my question. I saw one but I have no idea what I can do with. I am no wordpress expert.

I work since march on my website – wordpress with enfold theme, use custom css, change colours, type, … editor – footer, header and so on e.g. change copywrite, … and I don´t know how much changes more…?!?

But now I have to make an update for wordpress and enfold theme and saw – I did not create a child theme. So please help me. I do not know how I can make a child theme from my edited theme with all changes I made.

I have searched very hard all week long for all these changes. It would be a disaster if I have to do all things again.

So please I bet you to help me – step by step solution I can´t do that alone. I tried to find answers in internet. No way to find suitable solution because I wrote I´m not an expert.

Thank you in advance
Best regards
Marion