Apps are definitely the way to go if you're busy. I started using promova about four months ago and it fits perfectly into my schedule. I practice during my commute or lunch breaks for twenty minutes. The lessons are structured but not boring like textbooks. You can focus on specific areas like speaking or grammar depending on what you need for work. Consistency matters more than long study sessions so short daily practice works better than cramming once a week. My confidence improved a lot especially when speaking with international clients. Just commit to doing it every day even when you don't feel like it