So I'm a recent graduate and my first job as a software developer in a German company

The company that hired you knows that. Their expectations of you will be adjusted. You're not expected to churn out tons of code from day one don't worry.

1- What makes someone a slacker in software development teams? i.e. suppose that I'm in fact slower than my colleagues in writing code and not as productive as them due to lack of experience, would they consider me a slacker?

Being a 'slacker' isn't about being unproductive, it's about not being professional in how much effort you put into work. It's about not having work ethics. Typically a slacker will come in late or leave early, won't care too much about their profession and so on.

The fact you're slower than people because of lack of experience is expected, it means you're not as good of a programmer which is perfectly OK - they wouldn't expect anything difference and there is no reason for them to consider you a slacker.

2- If i'm in fact slower, is there something I can do to compensate for this?

Work harder, put in a lot of effort to learn how to get things done quickly. There are a lot of resources on improving as a software developer. Also, repeating myself from earlier being slower as a new junior employee is entirely anticipated on their end.

I'm mostly concerned of the daily meetings when everyone will mention all those amazing tasks they accomplished but I will only mention probably couple tasks or so.

The goal of the meeting isn't to boast accomplishments - it's so everyone in the company knows what other people are doing so everyone has a good grip and if someone has domain knowledge or insights into someone else's work they have a chance to discover that and share them.

So I'm a recent graduate and my first job as a software developer in a German company

The company that hired you knows that. Their expectations of you will be adjusted. You're not expected to churn out tons of code from day one don't worry.

1- What makes someone a slacker in software development teams? i.e. suppose that I'm in fact slower than my colleagues in writing code and not as productive as them due to lack of experience, would they consider me a slacker?

Being a 'slacker' isn't about being unproductive, it's about not being professional in how much effort you put into work. It's about not having work ethics. Typically a slacker will come in late or leave early, won't care too much about their profession and so on.

The fact you're slower than people because of lack of experience is expected, it means you're not as good of a programmer which is perfectly OK - they wouldn't expect anything different and there is no reason for them to consider you a slacker.

2- If i'm in fact slower, is there something I can do to compensate for this?

Work harder, and learn how to get things done quickly. There are a lot of resources on improving as a software developer online. Also, repeating myself from earlier being slower as a new junior employee is entirely anticipated on their end.

I'm mostly concerned of the daily meetings when everyone will mention all those amazing tasks they accomplished but I will only mention probably couple tasks or so.

The goal of the meeting isn't to boast accomplishments - it's so everyone in the company knows what other people are doing so everyone has a good grip and if someone has domain knowledge or insights into someone else's work they have a chance to discover that and share them.