It is a new or used bike? You have watched YouTube videos on how to adjust the headset and there is still play?
One thing that is not mentioned in some videos is that the end of steering tube needs to be approximately 3mm below the top of the stem so that the compression screw will tighten the bearing. If the steerer tube is too long, you end up merely tightening the top cap against the steerer.
Remove the top cap and see if the steering tube is not too long. If it is, you would need to add another headset spacer under the stem. Once it is the proper length, it requires very little torque to adjust the bearings. You only need enough to compress it and eliminate play. If you crank down on the top cap's screw, you will over-torque the bearing and the steering will not be smooth.