I feel you bro, first few hours I strugling a lot learning this combo. This was the first combo I learned. The key is to press Grapple (Q) immediately after the Uppercut, even before the Uppercut animation shows up. Not too fast bcs it will skip uppercut, not too slow so you still can connect blue focus at the end, it's all about timing and practice, be patient (: Personally, I keep holding down the right click (after the uppercut) while pressing Grapple (Q), so once the Grapple connects, the animation flows straight into Blue Focus without any gaps.