These look like some sort of tensile test on a ductile material which is loaded until it breaks.
In the experiment, it looks like the test rig has some "slack" which gets taken up when the load reaches about 25 kN. There may be some flexibility in the test rig that makes the slope of the elastic deformation different from the theoretical model of a perfectly rigid test rig, or you might simply have a different values of Young's modulus from the test material.
Quite likely the load is applied to the test piece in a different way in the FE model and the test. For example the test may be applying a relatively concentrated load via a pin through a hole in the specimen (and there may be local plastic deformation around the hole, the pin may be bending slightly, etc, etc), but the FE model may by applying a uniform tension across all the cross section.
The elastic limit is slightly different between the test and FE model, but the difference of 10% is nothing to be worried about. The experiment is done in the real world, not in some idealized environment where everything is known to 16 decimal places! If you are going to design some "real life" structure based on these results, you would probably have "safety factors" much bigger than 10% in any case.
At large displacements, presumably the FE model has some effect (material properties again?) which makes the load curve slope downwards, after some value of strain is reached. The test does the same thing but to a smaller amount.
You don't say what FE software you used, but you might have only defined the material properties up to the strain that corresponds to the deflection of 35mm. Make sure that Young's modulus doesn't suddenly jump to zero for higher strains in your FE model, or something similar and unrealistic!
The test specimen then suddenly broke. There is probably nothing in the FE model to represent that explicitly.
The general agreement between test and model is very good here IMO. You just need to sort out a few details. Either correct the test data for the defects in the test rig, or make a more detailed FE model that includes the same defects.