tweak twtb 11

Signed-off-by: Jin Mingjian <jin.phd@gmail.com>

Author: jinmingjian

_thisweek/2021-07-14-tw_11.md

@@ -14,7 +14,7 @@ In this week, TensorBase still merge the PRs in a relatively high speed thanks f
 
 The initial ClickHouse compatible timezone support to the Date/Time related types has been added. The initial ClickHouse compatible remote table support has also been added into the sources. We will soon provide in-TensorBase data importing experience for all users. Thanks for all core contributors of TensorBase!
 
-Internally, we are still actively investigating the performance of existed DataFusion engine. Some 4x-5x boosting are achieved for some parts of the hash aggregation operator. We hope to show more excited improvements in the near future of this summer.
+Internally, we are still actively investigating the performance problem of existed DataFusion engine. Some 4x-5x boosting are achieved for some parts of hash aggregation operator. We hope to show more excited improvements in the near future of this summer.
 
 In the Summer 2021 of TensorBase, the tasks about storage, distributed query, RBAC(Role-Based Access Control) etc. are well discussed and developed [in the progress](https://github.com/tensorbase/tensorbase/issues?q=is%3Aissue+is%3Aopen+label%3Achallenge%2Fsummer-2021). Join us!🏄🏄🏼‍♀