I decide to study in Canada& I decided to study in Canada. if both make sense, what's the difference? One is in present tense while the other is in past tense. /go off to buy some groceries & go off buying some groceries Likewise, what's the differnece? and is it natural? I wonder if you say go outsiding to buy some groceries. "Go off to buy some groceries" is in the command/imperative form. Bob: "We're out of milk. What should I do?" Bill: "Go off to buy some groceries." "go off buying some groceries" has no subject and so must be a part of some sentence. Bob: "When I get drunk I go off buying some groceries." "Go off buying some groceries" is not natural. It sounds better to my ear to say, "Go off buying groceries" in whatever sentence I try. /I wonder if you say go outsiding to buy some groceries. Not really. “Outside” tends to be out-of-doors, and as groceries are sold in the grocery market or super market, which tend to be indoors, outside and buying groceries don't work particularly well together. Hope this helps!