Hi @Domingos_SN,
welcome to KNIME Community Forum!
As you are just beginning with KNIME here is couple of links:
- KNIME Hub where you can search for KNIME Nodes and Example workflows
- KNIME Introductory course where you will learn the basis
Regarding your workflow:
1st - Preview is done only when you are configuring node so ideally only once if your file format is same every month. Keep in mind that performance of Excel Reader node is limited due to the underlying library of the Apache POI project (check Node description for more about configuration as well)
2nd - There are many nodes that filter rows. Filter Row is certainly one you can use but there are others as well.
3rd - After node is successfully executed (green light) you are able to see its results. Right-click on it and there you will see at the bottom number of result tables depending on number of output ports. This way you can see the results in every step and there is no need for something like “Visualization node”.
To write data there are many nodes. This depends on the format and location you want your data to be. Type “Writer” in Node Repository and you will see possible formats.
Additionally here are two topics where switch from Alteryx to KNIME was discussed which might help you:
Hope this helps you with your transiton 
Have a nice day,
Ivan