I know your worries, I was in the same case too.
2. To backup your store on Magento 1.9: data backup can be done through the control panel (often called cPanel or admin panel) of your hosting provider. Magento experts also provide a dev document about how to create a backup on Magento 1.x: https://docs.magento.com/m1/ce/user_guide/system-operations/server-backup-create.html
3. The popular way to do the migration is using an automated migration tool that helps you automatically transfer all your data to your new store with a high level of security and accuracy, without interrupting your current store performance. Especially, you aren't a tech-guru so this tool will be the optimal choice for you.
Basically, to perform the Magento migration, there are 3 simple steps:
If you need detailed information, this document about Magento migration will help you.
I understand your worries, am I will try to help you as much as I can.
1. For installation, you can refer to Magento guide, which tells you to step by step process of Magento installation