diff --git a/src/core/seller.cpp b/src/core/seller.cpp
index 634e585..ab83c55 100644
--- a/src/core/seller.cpp
+++ b/src/core/seller.cpp
@@ -12,7 +12,7 @@ Seller::Seller(const std::string& firstName, const std::string& lastName, int se
     numberOfOfferedArticles_ = numberOfArticles;
 }
 
-inline void Seller::setSellerNo(int seller_no) { sellerNo_ = seller_no; }
+void Seller::setSellerNo(int seller_no) { sellerNo_ = seller_no; }
 
 inline void Seller::setFirstName(const std::string& firstName) { firstName_ = firstName; }
 
@@ -20,11 +20,15 @@ inline void Seller::setLastName(const std::string& lastName) { lastName_ = lastN
 
 inline void Seller::setNumberOfOfferedArticles(int number) { numberOfOfferedArticles_ = number; }
 
-inline size_t Seller::getNumberOfOfferedArticles() { return articles_.size(); }
+int Seller::getNumberOfOfferedArticles() const { return static_cast<int>(articles_.size()); }
 
-void Seller::addArticle(Article article) {
-    articles_.push_back(article);
-}
+void Seller::addArticle(Article article) { articles_.push_back(article); }
+
+std::string Seller::getFirstName() const { return firstName_; }
+
+std::string Seller::getLastName() const { return lastName_; }
+
+int Seller::getSellerNo() const { return sellerNo_; }
 
 std::vector<Article*> Seller::getArticles(bool onlySold)
 {
diff --git a/src/core/seller.h b/src/core/seller.h
index 4ac6a98..eeeac29 100644
--- a/src/core/seller.h
+++ b/src/core/seller.h
@@ -22,8 +22,11 @@ class Seller : public Entity
     void setNumberOfOfferedArticles(int number);
     void addArticle(Article article);
 
+    std::string getFirstName() const;
+    std::string getLastName() const;
+    int getSellerNo() const;
+    int getNumberOfOfferedArticles() const;
     std::vector<Article*> getArticles(bool onlySold = false);
-    size_t getNumberOfOfferedArticles();
 
   private:
     int sellerNo_{-1};