I'm leaving For BLC in June to get my E-5. What can I expect there? Is it hard or challenging?

If it’s hard then your leadership failed you, you will be challenged remember there is no I in team, listen to your instructors they will not lead you astray

If you go there with the mentality to “get your E5” as compared being indoctrinated and earning the RANK of SGT. BLC may not be tough, but being a leader may. Always remember you’re not just a paygrade

Take this bit of mentorship for what it is...
Get away from writing as one speaks or texts... It is unprofessional and will not bode you well as an NCO! BLC will teach you the basics of the things you need to succeed as an NCO. It will NOT teach you how to become an NCO or how to be an NCO. Those are things you will need to seek on your own... As an elder NCO, would definitely suggest a writing course for your success! You will be writing many things, from counseling statements, to awards to recommendations, etc... And those are just as a junior NCO. Once you obtain Staff, your peers will notice poor writing standards and well, I’ll just leave that one rest... I want you to succeed, thus my bringing to your attention!
All the best in your academy education and I wish you nothing but the best in high marks and success! V/R, Jim