i have added too many subdivisions and do not know how to reverse these. i need help with this
this would help understand the issue
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Not a lot of context here so I'll offer this...
If this was recent try loading an autosave, from the file menu.
Otherwise depending what version you are running, you could use either the remesh modifier or go into sculpt mode and use the remesh tool. However If you have topology you you wanted to keep you'll lose that.