To get all column names of a Table in Oracle you can use the following snippet.
SELECT table_name, column_name, data_type, data_length
WHERE table_name = 'TABLENAME'
If you are using MSSQL, take a look at this snippet -> How to list all columns from a table in MSSQL
To get a list of all tables in Oracle you can use the following query.
SELECT owner, table_name FROM dba_tables
if your user does not have sufficient access rights to query dba_tables, you can try to query all_tables which will only show you the tables you are allowed to see.
SELECT owner, table_name FROM all_tables