Hello, for the feats, items, spells that improves the speed, it's only the land speed and so if it doesn't mention in the description also fly, burrow, swim, the bonus for the speed doesn't apply for the other speeds, is it right ?
Thanks for your future answer.
Yes. If the ability only increases 'Speed' without specifying a movement type, then it is only directly increasing land speed. For example, Fleet only affects land speed.
However, many other abilities give a different movement speed that is based on the creature's land speed. Increasing the land speed would also increase the associated speeds that are calculated from land speed. So for example, Strix Juvenile Flight would not be affected by a land speed increase, but Ranger Animal Feature would be.