I assume you mean the tier 1 investor visa, as you have a number of visa routes under the tier 1 plus now you have the newly introduced innovator route replacing tier 1 entrepreneur. If your enquiry is about the investor route, the Home Office should make a decision in three weeks. Regarding finishing the application quickly, completing the visa form online is not an issue. How you present your application to the caseworker is the key and ensuring you comply to the immigration rules as tier 1 Investor rules recently changed. Unless you use a regulated law firm, you should read tier 1 immigration rules and make sure you comply to the ones relevant to your application.