Hi. I’ve been using Blender for a while, but this is the first time I’ve encountered this problem. Yesterday Blender started lagging a lot for me. This makes it very difficult to use the program, and sometimes it is even impossible. It started with copying an object from an older .blend file to a new one I was just creating. I tried to fix it on my own, reinstalled the program, installed the latest version, installed the latest video card drivers, changed the Nvidia Control Panel settings. Nothing worked. On the internet I found information that deleting the “opengl32.dll” file may solve the problem, but I couldn’t find this file in the blender folder. A broken or slow computer is also not the cause as my computer works flawlessly as always and so do the apps that are installed on it. The lag issue only occurs in Blender. I don’t know what to do anymore. please help urgently
Welcome 
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…so after reading this this might just be a problem with this specific older .blend file ?? You didn’t provide any information about the size of your actual scene and also the old object. If you may have looked into this forum before registering you might know that this type of questions are… not so easy to solve for the community… and you may have to spend a little time to be able to upload images or blend files… see also…
( Not every time it’s the app or the OS or anything… lately something just didn’t worked in my browser… and guess what… i had to delete the cookie of this site… and the only one who is changing this… is this site… 
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So if you can’t give any more information about this i fear that it’s very difficult to help you right now…
Anyway… really made copy-and-paste between blender instances or appended or linked the file (for the later this might be a problem becasue of the newer version… ?? ← just an idea… so i suggest append… )
Hello. Thank you very much for your answer, I will try to provide as much additional information as possible.
When I created this older object, I had Blender 2.78 at the time if I remember correctly. Since then, I only open this file occasionally. Since the creation of this file, I have changed the blender version several times: 2.78, 2.8, 3.1, 3.5 (3.5 is the version I have now).
Every time I changed the version of Bledner, I opened the file and then there were no problems
The file weighs 58,714 KB
All objects in the file in the scene have a total of 313,156 vertices
There are three objects: Figure, Mantle and Armature
Both objects are attached to Armature, i.e. the objects are animated
Blender’s preferences are the default. The only thing I’ve changed is the settings to make Blender use my dedicated graphics card
Well, right now that’s all the information you might need
Hmm… if opened also before and not soo big then this indeed is a bit weird… 
because of the dedicated graphics… do have the rendered view now as default… so maybe it just takes a bit time to load and compile the shaders ?? (Somehow an almost wild guess… )…
Another thing which came to my mind… there seems to be a slighly difference between gaming drivers (newest fetures ) and “working” drivers (more stable)…
…and now i’m out of ideas 
Thank you for your answer. I’ll check my graphic card drivers again. If that doesn’t help, I’ll probably have to reinstall Windows