还行 is the classic Chinese non-committal answer - like English 'it's alright' or 'meh'. Often softer than 不错 ('not bad' = positive) but more positive than 一般 ('average'). The 还 here is the 'still / passably' sense, not 'return'.
mistakes
Don't read 行 as 'háng' here - that reading means 'row / profession'. In 还行 it's 'xíng' = 'okay / will do'.
