"But a lot of areas remain to be worked on. The next round will be tough and we must cover all grounds. We are getting there."
Sri Lanka, who failed to make the semi-finals in the inaugural T20 Worlds in South Africa in 2007, are drawn with Pakistan, Ireland and New Zealand in Group F of the Super Eights.
The other group has defending champions India, South Africa, the West Indies and hosts England, with two teams from each group advancing to the semi-finals.
"To win a world-class tournament like this, one needs to do well against all teams," said Sangakkara. "There are no easy groups, no easy games. We can't