I don’t have the same phone and it’s in general pretty difficult to fix a brick without being able to tinker with it. I can give you some pointers though…

First off, this guide is for a model A525F, but your title says your phone is an A526B. If that’s correct there’s a chance the files you tried to flash were for a different model number and that’s what went wrong. Make sure you download the right files for your exact model number rather than trusting the ones your guide provides.

Secondly, to be honest, this guide does not seem very trustworthy. When doing this kind of thing every little step matters, a single misplaced reboot might screw up the whole process. Also, you’re downloading and installing on your phone some files from some random website, that’s a big risk. The thing is: you don’t need a shitty guide for your exact model. For future reference, you’re better off with a good, detailed guide for your general vendor (Samsung). XDA forums are usually the place to look. Always find the files you need by yourself, don’t just flash whatever some random website makes you download. Go to the official download pages for Samsung stock OS or TWRP and get the files from there, making sure they match your exact model number.

If you’re 100% sure that the firmware you’re trying to flash is the correct one for your model, you can try avoiding Odin and use adb flash directly. There’s plenty of guides on how to do that going around. You might not need TWRP either at that point. Getting familiar with adb is always useful.