If a user plugs in a USB mouse and attempts to use it with Minecraft: Pocket Edition, they might not only face these issues, but the mouse might not even be recognized by the game in the first place and the game will not receive mouse clicks or mouse movement.
EDIT: While on a Galaxy S7 a mouse will popup and you are able to navigate with it, it is not using a built in game mouse. This causes certain parts of the UI to be completely unusable with the mouse.
Device: Samsung Galaxy S7 (SM-G930A)
Thanks for your report! This is however a Duplicate of MCPE-9815 – If you have not, please use the search function in the future, to see if your bug has already been submitted, as currently over 47% of tickets are being closed as duplicate.