BERLIN (Reuters) – Borussia Dortmund teenager Jadon Sancho scored twice in six minutes on Saturday to help his team to a nervous 2-1 victory over Mainz 05 that sent them back to the top of the Bundesliga. Sancho’s goals were enough to lift Dortmund, who were dominant in the first half but inexplicably eased off after the break, to 66 points with five games left to play. It leaves them two points ahead of Bayern Munich but the champions can move back to the summit again if they beat Fortuna Duesseldorf on Sunday. While the three points were crucial in their title race, Dortmund’s second-half performance triggered alarm bells. “Roman Buerki saved our three points today,” said Dortmund captain Marco Reus, referring to the Dortmund goalkeeper’s 87th-minute triple save. “The first half was absolutely good but the second half was scary. We had almost no scoring chances and we cannot be satisfied with it. We just gave control to Mainz. If you want to be a champion then you have to go beyond your limits.” Dortmund, eager to make amends for last week’s 5-0 demolition by Bayern, put in a whirlwind start and Mainz almost scored an own goal when Danny Latza deflected a Mario Goetze cutback onto the post in the sixth minute. Jacob Bruun Larsen twice came close before Goetze tried again in the 17th minute and found England international Sancho at the far post who drilled in for the lead. This was Goetze’s seventh assist this season, the most since the 2013-14 campaign when he was playing for Bayern. The 19-year-old Sancho then doubled the score in similar fashion in the 24th minute, firing in a Thomas Delaney assist that made him the youngest ever Dortmund player to reach 10 league goals in one season. The hosts, though, slackened after the break, allowing Mainz, who had hit the post on the stroke of halftime, to come forward. The visitors hit the woodwork again with Karim Onisiwo in the 63rd and cut the deficit with Robin Quaison’s deserved goal in the 83rd. Buerki then made his sensational triple save from point blank range three minutes from the end, including two stops to deny Mainz striker Anthony Ujah, and protected Dortmund’s invaluable three points.