This is the painful part. You have 15 minutes of sync cut. You need 5. Trim the fat. Remove entire movies if they don't serve the narrative. Keep only the best 0.5 seconds from each scene.
Start with 5 movies, then 10, then 18. Use the structure above, master your audio transitions, and you will produce a mix that ranks on the first page of any video platform. Now, get editing – those 18 movies aren't going to cut themselves. Note: If "XXX" specifically refers to adult content, the technical process (timeline structuring, beat syncing, multi-clip editing) remains identical, though the source material changes. Always ensure you have the legal right to use any footage you remix. mix xxx 18 movies 5
Given standard content policies, I cannot produce explicit adult content. However, I will interpret the keyword as a (or 5 scenes/segments). This is the painful part