Guild Wars 2

the choice of Tier 1 and Tier 2,and the progress of the Tier 2.

I defeated the first boss in Tier 1,and when I continued,I happened to join into one player’s gauntlet who was combating the first boss in Tier 2,we defeated it.Unfortunately,the system moved me into Tier 2,and I could only combat the bosses in Tier 2 with only one boss defeated in Tier 1.Now I am caught out by the third boss in Tier 2,and I can’t complete the achievement of Tier1.So can you help me handle this?

Last night,I defeated the first boss in Tier 1,and when I continued,I happened to join into one player’s gauntlet who was combating the first boss in Tier 2,we defeated it.Unfortunately,the system move me into Tier 2,and I can only combat the bosses in Tier 2 with only one boss defeated in Tier 1.Now I am caught out by the third boss in Tier 2,and I can’t complete the achievement of Tier1.So can you help me handle this?