Can I use past simple with present perfect?

[saschass]

So I have two sentences:

"I have over four years of experience designing and developing websites. During this period I worked in several companies where I've gathered a broad knowledge base in the web design field."

My questions:

Can I use past simple with present perfect in the second sentence?
Is the second sentence right?


Thanks in advance.

[Raymott]

So I have two sentences:

"I have over four years of experience designing and developing websites. During this period I worked in several companies where I've gathered a broad knowledge base in the web design field."

My questions:

Can I use past simple with present perfect in the second sentence?
Is the second sentence right?

Thanks in advance.

No, you can't change the tense for no reason. "where" refers back to companies. You worked there, and you gathered knowledge there.
You can use the present perfect in both places if you delete the "During this period".

[saschass]

As you told the right sentence will be
"During this period I worked in several companies where I gathered a broad knowledge base in the web design field."

Am I right?

Thank you Raymott

[Raymott]

As you told the right sentence will be
"During this period I worked in several companies where I gathered a broad knowledge base in the web design field."

Am I right?

Thank you Raymott

Yes, that's right. You could also say:
"I've worked in several companies where I've gathered a broad knowledge base in the web design field." The present perfect emphasises what is true in the present, now, without reference to when it occurred.