Hi ,
I am almost convinced, that based on your way of asking about fall(lowering)on 3 problem, you probably count waltz : 1,2,3 and know that you have to step on 1, to step on 2 and to rise , to close on 3 and to lower(fall). And your partner as probably more advanced dancer knows or just dance little more technical aspects.
I can suggest to start count music :(&)1&2&3&... and to clearly understand what you do on each half beat of music.
I will not explain what to do on 1&2& as it could take to much space here.
Your problem mostly connected with 3rd music count(beat), lets divide it on 3 and &.
On 2& you stand on ball of the foot , knee little compressed free leg is apart, as it was just pushing you during the 2nd step. So starting position is clear. On 3 you should use all your possible rises (foot rise, knee rise and body rise together to the highest possible position so you fill your body is straitening). This will close your free leg to standing leg on which you rise, you should keep your free leg ball of the foot in slight contact with the floor to resist to closing action of the rise in order to control timing. On (&) transfer your full body weight on closing foot(ball of the foot)ans with no hesitation low. Lowering action will be just muscle relaxation and will start new swing action of next step. Also, when lowering try to do it in vertical line, especially before stepping back. You have to keep your heel off the floor, to lower on the ball of the foot and just when you push yourself backwards, to roll standing foot from ball to hill. This happens when 1 strikes.
I also suggest not to look at technique books, people wrote them for professionals who clear understand principles of movement, they just described (not explained) reactions (and not actions).
The best way, of course, is to go to good female professional teacher and to take pro-am lesson (when she dances with you), so you will fill what to do and when.