Since this is so long, heres a summary, the fight is much easier if you've watched youtubers beat him before (or anyone really) then you could easily just do Bad Time Simulator (the replica of sans fight) and improve on that, then you can move onto the real game beat quite quickly like me on my second attempt. No footage but here are some helpful tips in this video (will upload it soon)

I can easily beat him, (no offense to anyone) it could be because i've watched a few youtubers do his fight first so i knwe what to expect, it could even be since i was starting it on bad time simulator (https://jcw87.github.io/c2-sans-fight/) which we can progress when we heal and it's not by toby. When i was doing genocide (on my xbox) i couldn't beat undyne so i went onto that and eventually tried doing geno on my laptop and beat it the same night i started, undyne was REAALLY difficult but i eventually beat her (props for this person with many tips (https://www.reddit.com/r/Undertale/comments/3m1fym/help_i_cant_beat_undyne_probably_at_around_70/) look in the comments for the guide for that) and then i moved on to core and passed through MTT NEO, went through New Home and got to the Judgement Hall, saved, went to fight sans, died quickly first attempt but then afterwards, on my secnd attempt brushed through the fight to the end with the gaster blaster spiral and had enough health to realise i would beat him and then i did.

Sorry this was so long