It isn’t safe everything has risks that come with it but recommended daily maximums in the USA I was last aware of are 600mg every 6 hours or 800mg every 8 hours, aka 2,400mg / 24 hours. In the past doses approaching that often included taking famotidine (pepcid AC) in an effort to reduce the ulcer risk that comes from it. There are also possible long term heart implications as other risks. Also never mix NSAIDs, non steroidal anti inflammatory drugs (don’t take ibuprofen with naproxen, diclofenac, etc). 800mg of ibuprofen is very unlikely to kill you taken one time during an acute event assuming you aren’t allergic to it or have taken something else that interacts with it. 800mg of ibuprofen taken regularly is likely to shorten your lifespan.