Fix some typos and clarify statements

Documentation/Administrator/Index.rst

@@ -22,15 +22,15 @@ Administrator Manual
 Installation
 ************
 
-It is strictly recommended to install this extension by using the composer.
+It is highly recommended to install this extension by using composer.
 
-There are two options to install the required packages solarium and symphony/event-dispatcher in non-composer mode:
+However, there are two options to install the required packages solarium/solarium and symfony/event-dispatcher in non-composer mode:
 
 a. Run the command "composer update" within the directory of the extension.
-   All the required packages are downloaded automatically to the vendor subdirectory.
+   All required packages are downloaded automatically to the vendor subdirectory.
 
-b. Download the required packages manually to vendor/solarium an vendor/symphony/event-dispatcher.
+b. Download the required packages manually to vendor/solarium/solarium and vendor/symfony/event-dispatcher.
    Please check the require sections (composer.json) of the extension, solarium and event-dispatcher
    to download and install matching versions.
 
-After the installation of the packages in non-composer mode you have to deactivate and (re-)activate the extension.
+After the installation of the packages in non-composer mode you have to deactivate and (re-)activate the extension in the extension manager to trigger the TYPO3 autoloader to rebuild the classmap.