Need help for assigning a variable with discord bot command

You can split your the message into an array of words:

const args = message.content.slice(config.prefix.length).split(/ +/).slice(1)

// example: `.boosting hello people of the world`
// returns: ['hello', 'people', 'of', 'the', 'world']

So, if you’d like to get the first argument (word), you can use args[0]. For the second, args[1], and so on.

You updated code:

client.on("message", (msg) => {
  if (msg.content.startsWith(config.prefix + "boosting" + " " + Variable)) {
    const args = message.content.slice(config.prefix.length).split(/ +/).slice(1)
    const embed = new Discord.MessageEmbed()
      .setColor("0xd08d11")
      .setTitle("**Random Title**")
      .setDescription(args[0])
      .addFields(
        { name: '\u200B', value: '\u200B' }, //spacer
        { name: "Person 0", value: 'Personvalue', inline: true },
        { name: '\u200B', value: '\u200B' }, //spacer
        { name: 'Price', value: 'Pricevalue', inline: true },
        { name: '\u200B', value: '\u200B' }, //spacer
        { name: 'Person 1', value: '40k', inline: true },
        { name: 'Person 2', value: '40k', inline: true },
        { name: 'Person 3', value: '40k', inline: true },
        { name: 'Person 4', value: '40k', inline: true },
      )
      .setThumbnail(logo)
      .setTimestamp()
      .setFooter('created by me or something like that');
    client.channels.cache.get(`here_is_my_channel_id`).send(embed); 
  }
});

client.login(config.token)