Herokuにデプロイ出来ません。

こちらを参考に作業したのですが、、Deployができません。
(https://qiita.com/ham0215/items/0cff5eb7d1398f70141d)

Deployまでは問題なくすすめたのですが、エラーが出てしまいます。

下記がBuild Logの一部エラー箇所だおもうのですが、対応方法がわかりません。
どなたかこうだよ！とかアドバイスいただければ。
よろしくお願いします。

-----> Building on the Heroku-20 stack
 !     Warning: Multiple default buildpacks reported the ability to handle this app. The first buildpack in the list below will be used.
			Detected buildpacks: Ruby,Node.js
			See https://devcenter.heroku.com/articles/buildpacks#buildpack-detect-order
-----> Ruby app detected
-----> Installing bundler 2.1.4
-----> Removing BUNDLED WITH version in the Gemfile.lock
-----> Compiling Ruby/Rails
-----> Using Ruby version: ruby-2.6.6
-----> Installing dependencies using bundler 2.1.4
       Running: BUNDLE_WITHOUT='development:test' BUNDLE_PATH=vendor/bundle BUNDLE_BIN=vendor/bundle/bin BUNDLE_DEPLOYMENT=1 bundle install -j4
       The dependency byebug (>= 0) will be unused by any of the platforms Bundler is installing for. Bundler is installing for x86_64-linux but the dependency is only for ruby, x86-mingw32, x64-mingw32. To add those platforms to the bundle, run `bundle lock --add-platform ruby x86-mingw32 x64-mingw32`.
       The dependency tzinfo-data (>= 0) will be unused by any of the platforms Bundler is installing for. Bundler is installing for x86_64-linux but the dependency is only for x86-mingw32, x86-mswin32, x64-mingw32, java. To add those platforms to the bundle, run `bundle lock --add-platform x86-mingw32 x86-mswin32 x64-mingw32 java`.
       Fetching gem metadata from https://rubygems.org/............



      Bundle completed (38.37s)
       Cleaning up the bundler cache.
-----> Installing node-v12.16.2-linux-x64
-----> Detecting rake tasks
 !
 !     Could not detect rake tasks
 !     ensure you can run `$ bundle exec rake -P` against your app
 !     and using the production group of your Gemfile.
 !     /tmp/build_6e46c8f1_/config/boot.rb:4:in `require': cannot load such file -- bootsnap/setup (LoadError)
 !     from /tmp/build_6e46c8f1_/config/boot.rb:4:in `<top (required)>'
 !     from /tmp/build_6e46c8f1_/bin/rake:2:in `require_relative'
 !     from /tmp/build_6e46c8f1_/bin/rake:2:in `<main>'
 !
/tmp/codon/tmp/buildpacks/50d5eddf222a9b7326028041d4e6509f915ccf2c/lib/language_pack/helpers/rake_runner.rb:106:in `load_rake_tasks!': Could not detect rake tasks (LanguagePack::Helpers::RakeRunner::CannotLoadRakefileError)
ensure you can run `$ bundle exec rake -P` against your app
and using the production group of your Gemfile.


 !     Push rejected, failed to compile Ruby app.
 !     Push failed