I'm assuming that you are actually asking about sound editing rather than mixing, so I'll reply on that basis:
It seems to me that you are visually focused and this is greatly limiting what your sound is able to accomplish, by that I mean limiting how much the sound is able to help your storytelling. The majority of film making is concentrated on what is happening in the frame but this is NOT the case with sound design. Sound Design concentrates on the story telling and in involving the audience not in the frame in which the characters are seen but in the environment and world which the characters inhabit. This might seem like an insignificant difference but it's not, it's a huge difference as it is likely to mean the difference between the audience just watching your film and your audience feeling involved in it.
For example, the only sounds we hear in the two clips you posted are the sounds which are the most obvious visually; a car door closing, a coke can being opened, some footsteps, the elevator doors opening, the cap being removed from a syringe, etc. The end result is that we (the audience) don't feel engaged in the scenes but we don't know why, we know something is missing but not what.
Go to a busy multi-story car park and spend 20 or 30 minutes with your eyes closed just listening to the environment around you. Echoey tire screeches, distant echoey bangs, crashes, shopping trolleys, voices, other indistinct mechanical sounds, distant traffic noise and other sounds from beyond the car park. To feel involved in the world/environment you are creating in your scene, the audience needs to hear that environment (and believe what they are hearing) so they feel they are IN that environment WITH the character/s, rather than just watching some footage of an unfamiliar environment which looks like a car park. Beyond creating this aural environment to involve your audience in each scene, you can use elements of that aural environment to highlight the emotions you are trying to create. For example, at about 0:32 in the kidnap scene, you could have a distant bang, tyre screech or some other car park sound. This sound doesn't need to be in your face, it's just one of the many elements of your car park ambience which luckily (!) just occurs at that point in time to heighten story, as your character looks around, wonders for a second if someone/something is there and then dismisses the thought.
If you haven't already seen it, can I suggest you have a read of this thread on
Sound Design Principles, which will give you quite a few pointers on how to use sound more effectively.
G
