Before installing the opencv file as in the instructions, you can run these commands:
apt-get -y purge wolfram-engine
apt-get -y purge libreoffice*
apt-get -y clean
apt-get -y autoremove
this will remove libreoffice and wolfram-engine.
Anyways this is strange as even I have it on 32GB sd card and it works fine.
I hope this helps!