You can’t “copy and past” new versions of the same data/log files, because sql server store logical information about -for example- the last transactions or blocks in the master database.
Instead of this, you can try to “detach” and then “attach” again the files. Doing this using the sql server management studio tool is quite simple:
to detach the database:
right click on the database you want to detach, “task” – > “detach”
to attach a new database:
right click on the “databases” folder, “attach”, choose the mdf file and the system will propose all the remaining files in the database (you can change the path of the files if you need to)