Website loading is terribly slow

[KoljaFrahm]

When I use yarn vite, the console is usually ready in around 3s.
When I then open localhost:3000 in the web browser, it takes around 1 min to actually load the site (even in a private window).
If I use vite preview everything is fast.
My app is quite big, but this is too long, isn't it? What can I do to improve the speed?
The request that takes the longest is
fetch("http://localhost:3000/node_modules/.vite/deps/recharts.js?v=307a82bc"),
then there are two more requests that take less than one second, the rest takes (mostly much) less than 60ms. There are 6049 request in total.
Dependencies I have:

  "dependencies": {
    "@mantine/colors-generator": "^8.0.1",
    "@mantine/core": "^8.0.1",
    "@mantine/dates": "^8.0.1",
    "@mantine/form": "^8.0.1",
    "@mantine/hooks": "^8.0.1",
    "@mantine/notifications": "^8.0.1",
    "@protobuf-ts/grpcweb-transport": "^2.10.0",
    "@protobuf-ts/runtime": "^2.10.0",
    "@protobuf-ts/runtime-rpc": "^2.10.0",
    "@react-keycloak/web": "^3.4.0",
    "@reduxjs/toolkit": "2.8.2",
    "@tabler/icons-react": "^3.31.0",
    "classnames": "^2.5.1",
    "clsx": "^2.1.1",
    "csv-file-validator": "^2.2.0",
    "dayjs": "^1.11.13",
    "i18next": "^25.1.3",
    "i18next-browser-languagedetector": "^8.1.0",
    "jwt-decode": "^4.0.0",
    "keycloak-js": "^21.1.2",
    "lodash": "^4.17.21",
    "mantine-datatable": "^7.17.1",
    "react": "^19.1.0",
    "react-dom": "^19.1.0",
    "react-i18next": "^15.5.1",
    "react-image-crop": "^11.0.10",
    "react-redux": "^9.2.0",
    "react-router": "^7.6.0",
    "recharts": "^2.15.3",
    "universal-cookie": "^8.0.1"
  },
  "devDependencies": {
    "@eslint/js": "^9.26.0",
    "@ianvs/prettier-plugin-sort-imports": "^4.4.1",
    "@modyfi/vite-plugin-yaml": "^1.1.1",
    "@protobuf-ts/plugin": "^2.10.0",
    "@types/lodash": "4.17.16",
    "@types/node": "^22.15.18",
    "@types/react": "^19.1.4",
    "@types/react-dom": "^19.1.5",
    "@vitejs/plugin-react": "^4.4.1",
    "eslint": "^9.26.0",
    "eslint-config-mantine": "^4.0.3",
    "eslint-plugin-jsx-a11y": "^6.10.2",
    "eslint-plugin-react": "^7.37.5",
    "node-protoc": "^1.0.3",
    "postcss": "^8.5.3",
    "postcss-preset-mantine": "^1.17.0",
    "postcss-simple-vars": "^7.0.1",
    "prettier": "^3.5.3",
    "rollup-plugin-visualizer": "^5.14.0",
    "stylelint": "^16.19.1",
    "stylelint-config-standard": "^38.0.0",
    "typescript": "^5.8.3",
    "typescript-eslint": "^8.32.1",
    "vite": "^6.3.5",
    "vite-plugin-svgr": "^4.3.0",
    "vite-tsconfig-paths": "^5.1.4"
  },

I already looked at https://vite.dev/guide/performance and tried to include the suggestions, but it doesn't help much.
I included recharts and other bigger plugins in optimizeDeps, this doesn't make a big difference.

Would someone be so kind to point me to how I can speed up the loading up the website?