initial commit to update marketo source doc

Author: terence1988

src/connections/sources/catalog/cloud-apps/marketo/index.md

@@ -275,36 +275,31 @@ Currently, Warehouses are the only supported destination for object-cloud source
 
 ## FAQs
 
-### How many API calls will the Segment source use?
+### How many API calls will the Segment source use to sync all my data?
 
-The Marketo API has different limits for the number of objects returned by different endpoints, but usually 100-300 objects per call.
+Segment couldn't provide the statistics regarding the number of API calls we consumed, becasue our systems only log the number of objects that we pulled from Marketo as throughput. 
 
-At set up time, you have the option to specify a cap to the API calls that our source can consume. If no cap is specified, we will by default consume as many API calls that are available to sync the entire source.
+### Could I limit the API usage on the source?
 
-We also use the Lead Activities bulk API to reduce the number of requests needed to sync the data; this however, also has a limit of 500MB worth of files downloaded per day.
+Yes, you have the option to specify a cap to the API calls that our source will consume per day. If no cap is specified, we will by default consume as many API calls that are available within your limit that you agreed with Marketo to sync the entire source.
 
-If your source requires more than 10k calls or over 500MB from the bulk API to sync, we will continue the sync the following day when a new batch of API calls are available.
+We also use the `Lead` and  `Activity` Bulk Extract APIs to reduce the number of requests needed to sync the data; this however, also has a limit of 500MB worth of files downloaded per day.
 
-If you have other applications that use the Marketo API, this can interfere with their ability to make requests.
+### What happens when my Marketo API limits daily quota is not enough?
 
-### What Marketo API are you using?
+If your source requires more than 10k Rest API calls, or over 500MB via the Bulk Extract API to sync, we will continue the sync when a new batch of API calls are available.
 
-We're primarily using the REST API, but also use the Lead Activity Bulk API to reduce the number of requests needed to sync.
+Please be aware that the Marketo API quota is available across your subscription, if other applications are sharing the quota, it will interfere with our ability to sync the source.
+
+### Why the `lead_activities` collections is not ingested by Segment? Why I couldn't find `lead_activities` table in my data warehouse?
+
+Please fill the Activity Type IDs (optional) setting in the Marketo source. It is required to pull the `lead_activities` collection source. Once Segment pulled data, the data will be availabe in your data warehouses shortly 
 
 ### Can I get other collections not default synced by the source?
 
 Yes! [contact Support](https://segment.com/help/contact/) to request additional collections.
 
 ### Can I get other columns not default synced by the source?
-Yes! For leads and activities, we've introduced a custom fields setting where you can enter comma-separated (no spaces, etc.) custom fields to sync by their REST API name.
-
-By default, we only sync the following fields on the leads collection:
-
-- id
-- email
-- firstName
-- lastName
-- createdAt
-- updatedAt
+Yes! For `leads` and `activities`, we've introduced "Custom Lead Fields (optional)" where you can enter comma-separated custom fields, which will be synced by Marketo's REST API name.
 
-You can find a full list of standard fields and their REST API names [here](http://developers.marketo.com/rest-api/lead-database/fields/list-of-standard-fields/). If there are other fields you're interested in, [contact support](https://segment.com/help/contact/)  for assistance.
+Full list of standard fields and Maketo's REST API names can be found at [here](http://developers.marketo.com/rest-api/lead-database/fields/list-of-standard-fields/). If there are other fields you're interested in, [contact support](https://segment.com/help/contact/)  for assistance.