To make/lose money hand over fist	acquire/lose a lot of money very quickly
To give sb a free hand	allow sb to do as they wish
(know sth) off hand	(know sth) without asking or looking it up
To fly off the handle	lose your temper very suddenly
To do sth at the drop of a hat	be willing/happy to do sth; do sth quickly
To make headway	make progress
To take heart from sth	feel encouraged by or optimistic about sth
To one's heart content	(do) as much or as often as one wants
To strike/hit home	trafić w dziesiątkę