If you can calculate but graphs confuse you, the weakness is probably representation rather than arithmetic. A graph compresses information into axes, scales, points, slopes, intersections, regions, and trends. If those visual relationships are not read accurately, correct calculation skills have nothing reliable to work on.
Practise reading before solving. State what each axis represents, check the scale, describe the trend in words, identify important points or intersections, and explain what a change on the graph means in the real situation. Only then calculate. This builds the bridge from picture to quantity.
Use the Mathematics Learning Hub for graphs and functions. If visual interpretation is failing across several topics, use the Diagnostics & Recovery Hub to locate the earlier representation gap.