Hello! The sentences are understandable, but it's a bit more natural this way: "If it's sunny, I get to work in about an hour. But if it's raining, it takes about two hours." Notice the contractions (it's) and using "get to" instead of "arrive" ("get to" is more casual). Hope this helps! :)

The sentence is mostly natural, but a few small adjustments can improve its flow: "If it is sunny, I arrive at work in about an hour. But if it is raining, it takes about two hours." Or, more concisely: "If it's sunny, I get to work in about an hour. If it's raining, it takes about two hours."