is it normal fps decrease when a texture is loaded to freeplay

The more things that are loaded: Textures, 3D items, Flames, etc... Will cause your game to run slower. I wouldn't say it's normal for it to run faster when textures load. If it's just a few it usually doesn't affect anything. But a whole body set can.

If your problem is speed, make sure your settings are set to low, and then If you'd like, mess with the advanced settings to pick and choose what you want and see if it makes your game slower or not.