Having trouble joining moves together

Can anyone tell me how to effectively join moves together? For example lots of challenges require joining various normal punches/kicks together, but I’m finding this very hard, for example :lp::lp::mk::hk: or something like that, the character simply can’t use them fast enough and Dan ends up blocking. The same applies to joining specials to kick/punches. I can’t even do a crouch :lk:-> light hurricane kick properly, there’s always a short pause in between the two moves which ends up being blocked.
Oh btw I’m using keyboard, so I just want to practice very basic combos, as there’s no way I can pull off those super-long combos with a keyboard.

Find the sub-board for the character you’re using and look for threads about combos and challenges/trials. Also look around for threads on plinking and links in the main IV board. It’s all in the timing.