Problems with maven in IDEA

I decided to take a course at stepic on developing a web server in java, but I ran into a problem-in pom.xml each plugin is highlighted in red in the list compiled by the teacher (which should work). Because of these problems, jetty and freemarker do not connect. The project uses this library and the template engine, but since they are not connected, IDEA does not understand where to get them in the source code when accessing them. Please tell me how to solve this problem problem?

Screen

Pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>

  <groupId>L1.1</groupId>
  <artifactId>L1.1</artifactId>
  <version>1.0</version>

  <build>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-compiler-plugin</artifactId>
        <version>3.3</version>
        <configuration>
          <source>1.8</source>
          <target>1.8</target>
        </configuration>
      </plugin>
      <plugin>
        <artifactId>maven-assembly-plugin</artifactId>

        <configuration>
          <descriptorRefs>
            <descriptorRef>jar-with-dependencies</descriptorRef>
          </descriptorRefs>
          <outputDirectory>${basedir}</outputDirectory>
          <finalName>server</finalName>
          <appendAssemblyId>false</appendAssemblyId>
          <archive>
            <manifest>
              <mainClass>main.Main</mainClass>
            </manifest>
          </archive>
        </configuration>
      </plugin>
    </plugins>
  </build>

  <dependencies>
    <dependency>
      <groupId>org.freemarker</groupId>
      <artifactId>freemarker</artifactId>
      <version>2.3.20</version>
    </dependency>

    <dependency>
      <groupId>org.eclipse.jetty</groupId>
      <artifactId>jetty-server</artifactId>
      <version>9.3.0.M0</version>
    </dependency>

    <dependency>
      <groupId>org.eclipse.jetty</groupId>
      <artifactId>jetty-webapp</artifactId>
      <version>9.3.0.M0</version>
    </dependency>

  </dependencies>

</project>