on sth's last legs	about to fail due to age/poor health etc.
put sth on the back burner	postpone sth till a later time
on the blink	not working properly
to weigh a ton	very heavy
kill two birds with one stone	fulfill 2 purposes with one single action
teething problems	difficulties that occur in the early stage of action
nuts and bolts	basic practical details
go on line	podłączyć się do internetu
as clear as a bell	very easy to hear/understand
surf the Net	look up information on the Internet to see what's available
make head or tail of	understand
mind-boggling	amazing or confusing
come in handy	be useful
see the light	understand after a long time
in the pipeline	in the process of being produced
to go back to the drawing board	plan again from the beginning
a flash in the pan	popular for only a short period of time
past its sell-by date	no longer effective/interesting
sell like hot cakes	sell many of sth very quickly
a carbon copy	sth that is exactly the same as sth else