Sorry but as has been mentioned a few times by a few people already, your first and best option is to optimise the models/meshes before you export them, using tools in Blender or whatever 3D software you are using to create the files.
You cannot easily optimise such large files in Babylon.js. It’s a case of “garbage in, garbage out” - ensure the files are optimised as much as possible following the advice of @Tricotou above, and only then will you be able to efficiently load them using Babylon.js and apply other optimisation techniques.