Exercise #3 Squats
As with lunges, regular bodyweight squats are often underrated. But they are such an important movement to learn. Once you do then there are hundreds of variations that you can learn to make them more difficult.
Stand upright with your chest pushed out, shoulders back, and feet slightly wider than shoulder-width apart. Turn your toes out slightly. Your arms can be held out in front of you for balance, or they can be by your side.
Keeping your heels firmly on the ground (especially important) you want to slowly push your glutes backwards; this will cause your knees to bend as you lower yourself down into a squatting position. Pause when your thighs are parallel to the ground, and then rise back upwards.
If you find that your heels keep rising, then you either have a mobility issue or a fear of falling. You can bring a chair in and place it behind your feet. Then when you squat you will be able to briefly touch the chair. This will help you with your form and get you to start performing the squat properly. It will also improve your mobility and strengthen your thighs, making real squats much more possible.