After many years (di' etōn pleionōn). “At an interval (dia) of more (pleionōn) years” (than a few, one must add), not “after many years.” If, as is likely Paul went up to Jerusalem in Act 18:22, that was some five years ago and would justify “pleionōn” (several years ago or some years ago).
To bring alms (eleēmosunas poiēson). Another (see proskunēsōn in Act 24:11) example of the future participle of purpose in the N.T. These “alms” (on eleēmosunas See Mat 6:1, Mat 6:4, and note on Act 10:2, common in Tobit and is in the papyri) were for the poor saints in Jerusalem (1Co 16:1-4; 2 Corinthians 8; 2Co 9:1-15; Rom 15:26) who were none the less Jews. “And offerings” (kai prosphoras). The very word used in Act 21:26 of the offerings or sacrifices made by Paul for the four brethren and himself. It does not follow that it was Paul’s original purpose to make these “offerings” before he came to Jerusalem (cf. Act 18:18). He came up to worship (Act 24:11) and to be present at Pentecost (Act 20:16).