there may be a more effecient way to do this, but this will work, and it will concatenate if there are multipul matches in one line

=CONCATENATE(INDIRECT("Sheet2!C"&MATCH(A2,Sheet2!A:A,0)),INDIRECT("Sheet2!D"&MATCH(A2,Sheet2!A:A,0)),INDIRECT("Sheet2!E"&MATCH(A2,Sheet2!A:A,0)),INDIRECT("Sheet2!F"&MATCH(A2,Sheet2!A:A,0)),INDIRECT("Sheet2!G"&MATCH(A2,Sheet2!A:A,0)),INDIRECT("Sheet2!H"&MATCH(A2,Sheet2!A:A,0)),INDIRECT("Sheet2!I"&MATCH(A2,Sheet2!A:A,0)))
it would run quicker on large ammounts of data if you add a helper column that contains =MATCH(A2,Sheet2!A:A) and just use the bellow, which is just a shortned down version. it is faster because the match will not need to be calculated as many times:

=CONCATENATE(INDIRECT("Sheet2!C"&B2),INDIRECT("Sheet2!D"&B2),INDIRECT("Sheet2!E"&B2),INDIRECT("Sheet2!F"&B2),INDIRECT("Sheet2!G"&B2),INDIRECT("Sheet2!H"&B2),INDIRECT("Sheet2!I"&B2))