There are standard 'red flag' behaviours that are the same for everyone, which you can google (like violence, name calling, coercive behaviour etc) but a healthier way to identify a red flag is 'Does this behaviour make me feel shit?' If you ask that, you'll filter out all the ones mentioned above, and you'll also identify your own personal red flags, for example you might not like sarcasm or being poked fun of, which might be a fun part of relationships for other people.
Relationships aren't hard. We have to make an effort sometimes, but the general picture should be 'I feel loved and supported by my partner' A good rule of thumb is 'A healthy relationship will never have you suspecting red flags, so if you're asking the question, it's not a healthy relationship.'
It's not about what a partner does 'right' or 'wrong'. There are no rules (except laws) The rules in your relationships are your feelings. So, if you feel lovely in a relationship, it's good for you. If you feel unsure/confused/wobbly/insecure etc, it's not good for you.
Genuinely don't know if this is normal behavior for someone
Forget normal. Nobody cares about normal. If we told you his behaviour was normal, would you feel you ought to just put up with feeling bad in the relationship? You NEVER have to put up with feeling bad in a relationship.
If you feel bad, you tell the person, and if they don't respect your feelings, you leave. That's all you need to know about boundaries, in a sentence, and it'll protect you from any abuse or poor treatment in the future.