I don't know you, so I have no idea. Your employer and colleagues could give you a better assessment. But I can say that an average grade taking the top classes at school is much better than average grades in the minimum-to-graduate classes.
Education doesn't stop with the degree. Good engineers never stop studying to expand their expertise.
I've been working for several decades with other engineers. It's not too hard to see who are the good ones and who aren't. The "aren't" are the ones who solve problems using trial and error, and when they get it to work they don't bother figuring out why it's working.
The "are" engineers will do whatever is required to find out what is actually wrong, work to understand it, and will do a targeted fix.
What kind of engineer you want to be is entirely up to you.
One thing you can do is take the youtube MIT CS courses. It's free. I've taken some of them to fill in gaps in my education.