Copying (!) Ver.1.6.1.3 to the newest version multilanguage

[Nina]

Hello,

I have an installed shop on a server. It is version 1.6.1.3, multi-languages (5 languages) and it looks very demode. Even I wouldn't buy from my store... I haven't changed it for many years.
As I have some free space on my host server, and I wish to "copy" the text and maybe all the pictures to the newest version. I don't have too much experience, therefore, I need your help.
On the same server, I have installed 2 additional sites, using Zen-Cart and WordPress.
Before taking any action, I'd like to ask several of questions:

1. Is this the best way to do it? I mean, making a new folder, rename it to beta.mysite.com, install a fresh installation + a new database for it, copying the text and using the same modules I have (newer versions) and then delete the old one and rename the new one to mysite? Is it possible to do it?

2. I don't know, but maybe I can change only the theme - but then I will have only to change or edit only the frontend pictures / details?

3. Will it have any influence on my product files too? I mean, do I have to write the text and place in each page the new / old pictures?

4. As far as I remember (it was really a long time ago), I had problems with the .hreflang.  I had to hire a freelancer to do it for me. Some issues with the way it shows on portable devices. So, the new theme will "destroy" the .hreflang and the way it shows on portable devices?

I will be very thankful for your help, as I am really scarred to do it by myself, and at the same time, I cannot permit myself to hire a freelancer.

Thanks in advance,

Nina