Mongodb .find() with opposite results

I have this get Request

router.get('/', async (req, res) => {
        //I connect to the DB and i return the collection with Posts
        const posts = await loadPostsCollection();
        res.send(await posts.find({ "tmima": { "$eq": 'andriko' } }).toArray());
    });

Everything works Fine as it is.. the problem is that i want to find the posts dynamicaly and not having this 'andriko' there.. I tried this { "tmima": { "$eq": req.body.params } } but its now working... the weird thing is that with req.body.params it shows all the other posts except those that have tmima: 'andriko'

This 'tmima' value comes from the dynamic route so thats why i need this req.body.params or something similar, to show the posts based on the routing.

Thx in advance!

EDIT!! FronteEnd section included!!

router.js

const routes = [
  {
    path: "/",
    name: "Home",
    component: Home,
  },
  {
    path: "/katigories/:tmima",
    name: "katigories",
    props: true,
    component: () => import("../views/katigories.vue"),
    children: [
      { path: 'anakoinoseis', name: 'anakoinoseis', props: true, component: () => import("../views/Ypokatigories/Anakoinoseis.vue")},
      { path: 'roster', name: 'roster', props: true, component: () => import("../views/Ypokatigories/RosterView.vue")},
      { path: 'vathmologia', name: 'vathmologia', props: true, component: () => import("../views/Ypokatigories/Vathmologia.vue")}
    ]
  }

axios.js

import axios from 'axios'

const url = 'http://localhost:5000/api/posts/';

class AnnouncementsService {
  //GET Annaouncements
  static getPosts() {
    return new Promise ((resolve,reject) => {
        axios.get(url).then((res) => {
            const data = res.data;
            resolve(
                data.map(post => ({
                    ...post,
                    createdAt: new Date(post.createdAt)
                }))
            );
        })
        .catch((err)=> {
            reject(err);
        })
        
    });
  }

Anakoinoseis.vue

<script>
import AnnouncementsService from '../../store/axios'

export default {
  name: 'Announcements',
  props: ['tmima'],
  data() {
    return {
      posts: [],
      text: '',
      title: ''
    }
  },
  async created() {
    try {
      this.posts = await AnnouncementsService.getPosts();
      await console.log(this.tmima)
    }catch(err){
      this.error = err.message;
    }
  },
</script>