Recently bought a 2006 Jimny, fuel gauge seems to drop by 1/5 each time I get in the car help!

Today I drove roughly 30 miles at the very most and my tanks dropped by a quarter is this normal?

The gauge the first 10-15 miles or so was still at full as very barely dropped onto the full line. I return to my car 30 mins later and out of no where it’s dropped a ton. Park up less 10 miles later, return to my car and it’s dropped down to quarter of a tank and has stayed there 10 miles later at home.

Used some RedX to clean out the fuel injectors. No obvious sign of a leak on the road or around the fuel tank under the car.

Sometimes when turning on or turning off there will be a strong smell of fuel for 30 seconds or so but isn’t clear where it’s coming from.

Is this a known issue with Jimnys?

As it stands it’s costing me almost a 50p a mile to drive which seems alot