Blogging on Blogger is risky because they can just wake up and decide you there your blog is deleted due to policy violations, so i recommended to blog on a paid hosting service like Wordpress which is almost the best.
Here are the steps to backup your blogger blog
1 Log into your blogger blog, on your dashboard click on Settings
2 Scroll down and select Basic panel, look for ‘Export Blog’ on the list of blog tools
3 Click on the Export Blog and choose where you want to save the exported .xml file (usually oped with Adobe Dreamweaver to your hard drive or exporting to another blogging platform like wordpress..
Ensure that is saved on a secure location, because this might come handy in situations when you accidentally delete some old blog post or if Blogger selects your blog due to policy violations now you have a copy of all your content that you may publish elsewhere.