Don't worry about trying to figure out the "correct" knee bend (not "knee lift") and foot lift. If you want to test how well knee lift works, run in place, and start lifting your knees higher, you'll find that it pushes the body backwards... this is generally not the direction we're trying to run. So knee lift is counter-productive.
In any case, your stride should feel relaxed (after some practice).
Anyway... do be relaxed. Relax the knees, relax the ankles, relax the hips, and lift your feet. The ankles, knees, hips, etc. will do what they need to lift the foot off the ground. The trailing lower leg should be just about horizontal as it swings forward when we're running really fast. This will adjust as we slow down.
But, don't worry about all of that, instead try focusing on the goal of running and walking, which is moving the body forward.
Now stand upright, bend your knees, keep the torso vertical, and move your vertical torso forward, allowing on foot to stay on the ground trailing the body, until it becomes necessary to lift that foot.
The idea is that we're going to be using the natural springs in our legs to propel us forward naturally, instead of "working" to run.
In order for these natural springs to work, we must land with bending knee, so that as the body lands, it loads the spring (bending the knee more), and as our body moves in front of our foot, the spring releases (naturally, no need to try to push) propelling us forward. It is essential to keep the hips low so that our trailing foot can stay on the ground pushing us forward until the leg is stretched out (do not try to stretch the foot out, or you may end up with abrasions and blisters on the toes). This is where you pick up the foot, the whole foot (not only the heels - again we don't want abrasions and blister on the toes).
In the meantime, the forward foot should be moving back, as the knee bends, so that when the foot lands, it is just barely in front of the body, and traveling backwards at the same speed as the ground is traveling under our body. Remember not to try to launch the body up, the hips need to stay low, so that our springs load, and can release behind us.